If by "ally" you mean countries that toe the US line like Mr Blair did back in the dodgy WMD dossier days, then India would prefer being "un-allied", thank you.
If you view the glass as half-empty, you can cite India's coziness with the erstwhile USSR, its failed market-socialist mixed model, trade barriers, etc.
But if you view the glass as half-full, you can look at India's reforms since the early 90s, opening up of its markets to western companies, replacing the lovey-dovey relationship with Russia with a more balanced approach that treats Western viewpoints and interests with due respect (e.g. India's vote against Iran) and the willingness to take risks to further the relationship with the US (e.g. faceoff threats from the Communist party in the Indian coalition govt and go ahead with the nuclear deal).
True, we can do better in many ways, but India is most certainly on the right track and thankfully, the US govt realizes that, terming India as a "natural ally".
IMHO India should go ahead with the missile shield if offered, even without ToT. In addition to obvious protection from potential threats from Pakistan and more importantly, China, I bet it offers long-term savings in running costs of maintaining air-defence forces on two fronts. There may be some analysts who have done the NPV analysis on this aspect and I would be interested in looking at the numbers...