I have a tmob nexus one using GV, and i use GV on my at&t blackberry, and iphone...there are no unexpected charges, but what you need to know is that GV is not a true VOIP capability like skype. Even tho they give you a #, the phone calls are still routed through your AT&T voice plan, not 3g(data). What happens is that when you place a call thru GV, request is sent to GV over data, and then GV calls you on your phone(even though you dont see this happen) and then your phone answers, and then GV dials out to the # you wanna call. So essentially, you are charged on all calls placed using GV as an incoming call...which does indeed count against your minutes, just as if you were to answer a call from anyone else calling your phone. The only way to not get charged for these calls on your minutes that I have heard of is people using tmob 5 favorite plan where they can add their GV # as one of their favorites. Otherwise, with AT&T, using GV will not save you any money on your minutes, what it WILL save you is that you get free texting with GV(since texts are all data). So you don't need a texting plan, just voice and data. Anyway, thats the skinny on GV...they bought gizmo5 a while back so i think they have plans of rolling out skype functionality soon, which will enable us to drop voice plans all together, and just have straight data on our android phones, and route all our calls through our data. That being said, GV is the greatest service i have ever had on a cell phone, and I will NEVER use a phone that is not GV compatible. It is so great to know my # will never change, and that i can change cell phone #'s all i want and never have to tell my friends my new #. Also, having calls ring all my phones is great. I am constantly amazed how little people know about this great service...it seems like only tech savvy people understand it/use it. I <3 GV!!!!!