Does the Rogers' 920 work 100% with T-Mobile, or just in refarmed areas?
^^ Yep. This is the reason you don't take your chances with an unlocked AT&T 920, theres no guarantee its going to work 100% the way it should. Get a phone with the proper bands for nationwide/complete support. 1700/2100 bands will get T-Mobile users full HSPA+ and LTE compatibility.