I had the smoothest upgrade imaginable at the Apple Store in Montgomery Mall, Bethesda, MD.
The day the phone was announced, I "reserved" a new 3G-S 32gig phone by specifying I wanted to add a new line, via the Apple Store website. My real plan was to add a line for my 14-YO son, give him my current 16gig 3G, and take the new phone for myself (since at the time I "reserved" my phone, AT&T wanted $500 for a straight upgrade). I also planned to get an 8gig 3G for my wife and add her (my 16-YO and I got our iPhones last August, but my wife and 2nd son were still on Verizon).
I'd gotten an email confirmation of my reservation immediately, and a reminder email yesterday, telling me I could go to the store anytime today. I went around noon; they had a concierge outside the store separating people into various lines. Since I had a reservation, she checked me on her list and directed me to a line with only one person ahead of me. Less than three minutes later I was escorted inside the store by a rep to begin the process. I was taken to a station where the phones were on a cart, and the guy there checked his list and then gave my rep my phone. When I explained the swap I wanted to do, the rep said he thought I'd have to take the new phone to an AT&T store to do what I wanted, but said since AT&T had changed their mind on the upgrade policy, I could simply upgrade my existing phone for the same $299 I was going to pay if I added it as a new line.
I said fine, but asked if I could also get two $99 3G phones and port numbers from Verizon. He said he didn't know, but would check, but another rep overhead me asking and said to my rep, "sure you can do that, just go in the back and grab two 3G's.". To do the porting, the guy needed my Verizon account #, which I didn't have, but he patiently waited whil eI called Verizon to get it. Less than 30 minutes later I left the store with my new 3G-S, and two new $99 3G's, all ported and activated and ready to go. I did end up buying an extra $99 phone, but I'll eBay my 16gig phone, s/b able to get $50 for it (it's mint), after which I'll have only spent $50 more than I planned to.
From the time I arrived at the concierge to the time I walked out the door took less than 45 minutes, and that was for three phones, two of which had to have numbers ported from Verizon. It was one of the two or three best customer experiences I've ever had. Even my 10 YO is happy, because he got my 14 YO's iPod touch!