I have T-Mobile, so naturally, I want to buy an iPhone and unlock it (or just buy an unlocked one). However, I was wondering what that does to the warranty and everything on the phone. I've had trouble in the past unlocking a phone and being deserted when it eventually broke but still would've been under warranty. And info would be greatly appreciated. Thanks!

Get a new HTC Diamond Touch. It beats the heck out of the IPhone and you don't need to put up with the Steve Jobs crap. You buy it, you pay for it, you own it and you can do whatever you want with the Diamond. Besides, it's a beautiful, powerful, Pocket Personal Computer not just a fancy cell phone. You don't need some egotistical CEO's permission to install new programs.
http://reviews.cnet.com/smartphones/htc-touch-diamond/4505-6452_7-33089238.html
Hope that helps.