Quoting ardichoke

If I get the G1 or the myTouch and don't like T-Mobile... well... by the time my contract is up there will be Android phones on most other carriers. Everything follows me. No hassle.

Could you elaborate more on how everything follows you? For example, how does purchasing apps work? If you buy an app for your G1 and switch to another Android device with another carrier, are those apps tied to your old G1, or to your Google Account or something?

If it's the latter and I get to keep the apps I've purchased and move them to other phones later on, that's a huge thing to me. But if it's stuck to the G1 or even T-mobile, not so much...