I've had two experiences with this store - the first was bad, the second was adequate.  I went in to the ATT store about 2 weeks ago to upgrade to the Iphone 4 and join a family plan with a friend.  The sales associate at the time seemed to know what he was doing and set it all up - told us it would take up to 3 days to get the plan together and that he would call us both when it was done.  A week later and no phone call, I went back to the store and talked with another associate who informed me that nothing was done since my first visit and in fact nothing needed to be done, that I could have an Iphone in 20 minutes and sure enough 20 minutes later the plans were set and the numbers were together on a family plan.  Overall the experience wasn't a good one, in that I had to wait an extra week for nothing, and was told misinformation from the start (plus the wait times were an hour one time I stopped in).  I'd suggest another store to upgrade or change plans.