Yes, I ported my AT&T number successfully. There was a bit of a problem in that the AT&T number was under my wife's Social Security number (we were on a family plan) and I signed up for T-Mobile using mine, so the automatic porting didn't work, but everything was fine after I called customer service. There was a period of a few hours where I had to carry both phones -- incoming calls went to my AT&T phone but I could make outgoing calls from the Nexus One -- but when that resolved, there were no further problems.