I went from Sidekick LX to G1, because a small business I ran on the side heavily depended on AIM, I was VERY dissapointed with the phone. I had non stop dropped calls, and the pgone was very buggy, and the AIM feature was TERRIBLE!!. I still have it, but, I bought an Iphone and unlocked it to use for T-Mobile. The reason I kept the G! is because the OS is open source, and I am sure that people will eventually come out with some good things for it, but until then I will use the Iphone, it is superior.
The G1 is a media phone, if you need a phone for bus. or anything of taht sort, I do not recommend the G.