Any downfalls to unlock/jailbreak Iphone 3gs??

My mom has a IPhone 3gs that she said I could have. I am on TMobile and would have to unlock/jailbreak it, I guess. I'm just wondering what kind of kinks I will run into if I do it. How do I get apps if not on the att network?

 

you will void warranty, but apps are all available.

 

I think gizmodo had a good guide if I remember right.
I don't know if being on tmobile blocks you from anything, but I don't see how. When you are on ATT, you get the App Store and Cydia.

It's a 3gs hand me down. I doubt there's any warranty left.

 

Can I still use Itunes w/ it?

 

I have an Iphone 3gs on tmobile.. Works great, but know that you can't run on 3g. Still works great though. Itunes works with no problems.. Depending on the firmware u may have to use an Ipad base band to unlock. just make sure you don't upgrade the phone. or you'll be stuck with a brick.

 

had a buddy jailbreak his iphone and every since then ran into problems with the software crashing and a lot of lag