Buying an Unlocked White Blackberry Pearl! Help!

So my girlfriend has finally converted to a blackberry, after much persistence on my part. My question to everyone (or anyone willing to help for that matter) is, I'm using AT&T and buying her an unlocked White Blackberry Pearl for T-Mobile to use on AT&T's network as well. Now I know it can operate on the network but what features (if any) will I sacrifice or will be disabled in any way on the phone. Obviously AT&T doesn't have my faves and things like that, but what else need I watch out for? Any help is greatly appreciated, and my apologies if this has been posted before, but I didn't find anything that related too much.


The phone is an unlocked Rogers phone as well if that helps. Info I just found out about...so not T-Mo I guess? Or?

Thanks.

Chris---