Genuine question: Why don't you buy an unlocked phone and use a prepaid plan on tmobile or something (assuming they are good in your area). You'll save a lot of money over 2 years.
I just don't have the money to pay upfront for a phone right now. If I could wait a while I would. The phone I have now is just about dead. The display lost its backlight and its ability to, ehm, display. I'm pretty much restricted to just answering calls. Otherwise, I have considered going with StraightTalk. (We may, however, visit this topic again.)
StuG, as for the various OSes, I haven't tried any of them, but from what I have seen I prefer Android over the others. Mostly because of under-the-hood things that really wouldn't affect the user experience. And, I really don't feel like driving for an hour just to find out which interface I like better. As long as it works, I'll be happy enough. And, on principle alone I will not get an Apple.