First off, GO WITH AT&T! If you want a full keyboard, go with the Palm Centro or BlackBerry. Also, depending on where you live, try going to a Best Buy (not a Circuit City or any other store, but Best Buy) because when I went there, I got a really good deal for my phone.
PS- Do NOT get the BlackBerry Pearl. It stinks to the high heavens! Get the REAL BlackBerry.

Oh, and GO WITH AT&T!