I went to my local Apple Store yesterday and asked for a 4GB, 1.6GHz 11" Air and got a bit of a blank stare from the salesperson, who said they only had the two models listed on the little card, which were the two stock 2GB versions. I asked her to check to be sure. She asked a number of other people who all shrugged their shoulders and then went into the back room. She came out a couple minutes later carrying a 4GB, 1.6GHz 11" Air.
I'd recommend that anyone who's being told by their local store that they're not carrying the high-end configurations - make sure they really know if that's the case. Some of them may just not know what they've got.
Wow, I didn't realize they carry the high-end configurations. I was going to order an 11" Ultimate online. Thanks!