This is more of a precautionary entry. I've been looking to get a Blackberry Bold 9700 for a little bit now, and checked a few things on it. I use T-Mobile and the main reason for getting the 9700 instead of the 8900 is simply the 3G aspect of the 9700. As of this posting, the BB 9700 is around $400 on ebay. If you use T-Mobile, or even if you don't, the best Blackberry 9700 to get would be the T-Mobile version.

The T-Mobile version is the only version that will work with T-Mobile's 3G network. If you buy an unlocked AT&T 9700 it WILL NOT WORK on T-Mobile's 3G. The T-Mobile 9700 WILL WORK on AT&T as well as T-Mobile though. So if you use T-Mobile, do not buy a Blackberry 9700 unless it's the T-Mobile version. The T-Mobile version will also work with AT&T 3G network as well. So if you use AT&T, it doesn't matter whether you buy an unlocked T-Mobile or AT&T Blackberry 9700.

T-Mobile's network uses the 1700 and 2100 mhz bands for its 3G network and REQUIRES both of them on a phone for it to work with the 3G. If it only has 2100, it won't work on T-Mobile 3G.