I am wring this to explain the situation to everyone here whether pro or anti deal. It is natural to have different opinions on different matters relating to the country. After all humans are political animals (Aristotle). But national decisions have to take one form or another. This implies not every one will get what he or she wants. We have to learn to live with different opinions and respect them. Calling people of different opinion, traitors and liars is not appreciated.
Life is not perfect. You have to deal with situation that fate has brought you. When life hands you lemons, make lemonade. The choices for Iran were two at its most basic level:
One) Iran continues on the previous path; either eventually becoming nuclear armed or just accumulating 20% enriched uranium and a few kilograms of plutonium without becoming nuclear armed. Risking even heavier sanctions, embargoes, isolation and pressures including even limited air strikes or even full war (specially if Iran does not become fully nuclear armed to deter attacks and ridiculously insists only on enriching uranium; much like a person who insists on producing and storing TNT in his house basement in huge quantities and claiming he is against making bombs on religious grounds).
Two) Iran makes a deal, keeps its expertise, capability, nuclear infrastructure and R&D in return for complete removal of sanctions and politico-economic containment of Iran. If sanctions are not removed or if the other side starts playing cat and mouse then the situation can go back to option one. Iran has chosen this path with the deal.
Here are some reasons why.
A) Majority of Iranians do not want Iran having nukes. And this is mostly because of the Fatwa effect. But still, the results have political implications. Both internally as well as externally (you can not expect other countries have any positive view of Iran acquiring nukes when Iran's own population does not want it):
Iranian population's view on a nuclear armed Iran:
Some other country's view about a nuclear armed Iran:
B) There are really only two scenarios along with their benefits and costs if Iran does not negotiate and does not accept a deal (which by definition means giving up something in return to get something else).
1) If Iran develops nukes:
The benefit of strategic immunity from invasion by regular forces of an enemy and national prestige of being nuclear armed. The cost is going to be increased pressure of various natures like political (through UN/Diplomatic Structures/NGO's etc) economic (through sanctions/sabotage), proxy warfare (through Takfiris/ MKO/ Seculars/ Modified Shias), propaganda (through Media/ Personal contacts), embargoes (through travel bans/ interception of Iran's shipping/ refusing Iranian airlines) etc etc.
2) If Iran does not develop nukes and only enriches uranium per its own wishes:
The benefit is only going to be a little national pride (since Iran will not be even nuclear armed). Cost is going to be increased pressures as above as well as the real chance of attack on Iran whether a full occupation or a partial occupation or limited/ long term air strikes on Iran's nuclear facilities, industries, power plants, military units etc etc.
C) If on the other hand, Iran accepts some voluntary measures according to a deal of give and take which are basically formalities since Iran did not already have nukes to begin with and officially did not even want them, then this is the cost vs benefit scenario:
Cost: If out of the blue a country launches a surprise and overwhelming conventional attack on Iran, then Iran will not be able to deter such an attack. The chances of this realistically is low as of now. Another cost would be if a nuclear armed country decides to nuke Iran, there is nothing with which Iran can deter such an attack. Again the chances of this realistically is low as of now.
Benefit: Iran will gain access to world's markets and can trade. Some pressures will remain but at a minimal and tolerable level. Iran still will be able to enjoy its little national nuclear pride. Iran will have the option to go fully nuclear and become nuclear armed within a year or so, as of now and probably within months after ten years when Iran's nuclear industry grows.
I will expand on some of these dimensions below:
D) The political benefits of this deal are many. Iran has played and won the equivalent of a political chess. By agreeing to this deal, Iran put all the pressure on West. It will be Obama and other Western leaders who will have to convince congress and Israeli/Saudi lobbies. It will be the Western media that will have to sell this deal to their public after decades of propaganda against Iran and demonizing Iran. In addition, Israel and Saudi states lost alot of prestige and national power, getting dumped by their main ally and protector. Saudis specially will be vulnerable because unlike Israel, they do not have any nuclear infrastructure and depend entirely on American geopolitical power to protect their monarchy. That is why any understanding between Iran and US will be seen in Riyadh at the cost of Saudis.
Another aspect of political benefit of this deal will be of a more complex nature. Before Iran had any serious nuclear program, the country was vulnerable to pressure tactics of sanctions and embargoes under various titles such as democracy, support for terrorism, human rights, women rights, protection of secularism, not respecting West's strategic interests etc etc. There was no way to satisfy these unless Iran became subservient to West completely or alternatively Iran completely destroyed. The nuclear issue though could be partially sacrificed to block these pressure tactics. Now as long as this deal is operational, Iran can not be sanctioned in a major way for any reason.
Since any new sanctions on Iran will be interpreted by Iran and by the rest of the world outside West as a cheap tactic to scrap the deal, forcing Iran to cancel the deal. In effect Iran's nuclear program now has become a deterrence against sanctions and pressure tactics against IRI. Not much different than nuclear weapons deter military attack except here the objective is not to deter military attack but non-military pressure tactics. It should also be noted that even military attack is rather ruled out by this deal since the reason for this deal was to prevent a war and if ever West tries to disregard the main reason of this deal, again Iran can easily and justifiably cancel the deal and make nukes (with full sympathy of the rest of world).
E) Economic benefits of this deal are also many. Iran needs alot of stuff that can not make locally and needs access to global markets to improve the economy both in size as well as in efficiency and socioeconomic justice spheres. Isolated economies specially the low technology economies seldom perform as well as those connected to the rest of the world. A strong case can be made that Iran's economic problems are due to local mismanagement which is actually true. But even a mismanaged economy that is richer is preferred to one that is poor. And it should also be noted that mismanaged economies take a long time to be corrected but it is easier to correct them when such an economy is not under various pressures.
Another aspect of economic benefit is in geopolitical terms. If Iran gains access to oil and gas technologies and can export oil and gas then the global prices will go down and the share of Saudis and Qataris in the market as well as their income decrease. This is an indirect benefit to Iran since as Iran's economy grows, those of its adversaries falter.
In immediate term, some 150 billion dollars of Iran will become available which is a huge amount for any country (Greece is fighting to get a deal for a few billion dollars in comparison). In the next five years, if Iran just exports on average 70 billion dollars extra on top of what it is exporting now, this comes to 350 billion dollars extra on top of the current exports of Iran. Combined this comes to 500 billion dollars extra cash in a five year period. Even now Iranians are not dying on streets of hunger and are surviving. So this 500 billion dollars is on top of mere survival subsistence. This is a huge financial power which can be put to use.
F) Iran will be able to gain access to non-military technologies it needs. In this area, Iran can use Europe as the provider of these technologies. The economy of Europe is in serious trouble. And Iran has 500 billion dollars extra money to spend in the next two years. Even if Iran goes with half of this money to Europe and shop for civilian technologies which Iran needs, almost all of Iran's problems in civilian areas can be solved since Iran already has a very highly educated workforce. Europe is also going to be happy since it will get paid top dollars. Just one example here about such civilian technology is modern water management systems for agriculture.
As you know Iran is in serious water deficit conditions. About 90% of Iran's water is used in agriculture. Modern agricultural techniques and water management systems can easily reduce water requirement by several times. Even if Iran reduces its water requirement in agriculture to less than half while increasing agricultural production by 30%, Iran's total water requirement will be reduced to about half of today. This will make Iran a water neutral country with complete food security. This is possible, just needs technology which Iran does not have. And Europe has that technology. Other areas of civilian technologies of interest can be Japanese car and electronic industry and German engineering technologies. Leave the French out this time.
G) Iran will also get access to conventional military technologies which Iran badly needs. Iran's air force needs new planes. Since West will not cooperate in this matter, only China and Russia remain. Both are in final stages of development of their 5th generation fighter. A serious negotiation can be had to get a good deal from them. Shah had purchased about 78 F-14s in 1970's and these have protected Iran till now and will still protect Iran in 2020's if no new purchase is made. That is over 50 years. If Iran buys a substantial number of 5th generation fighters, Iranian airforce will remain relevant in the region till towards the end of this century. And Iran has money to pay for it. For example Sukhoi PAK FA, costs about 100 million dollars a plane. Even if Iran does a deal for 200 of these, it will come to 20 billion dollars. Which is affordable for Iran. In fact at such a price tag, Iran can do a similar deal as India has done and get technology transfer and production license. Other military areas of interest will be stuff like Chinese frigate and destroyers like type 054A and Russian Lada class submarines, Russian or Chinese air defense systems and tanks, APC's etc etc.
H) Finally if push came to shove, Iran can always reset the clock to zero, cancel the deal and go back in time. If this happens for any reason in ten or fifteen years time, at least Iran will have enormously benefited in above mentioned ways.