The problems they’re seeing sound eerily similar to those we’re experiencing with our machines: Wi-Fi will initially connect, but after a minute or two the connection will stop working, and a total reboot is needed to be able to connect again. The problem is made worse when the Air is on a desk, quite possibly something to do with the Wi-Fi antenna being (*we think*) in the black plastic strip along the bottom of the screen.
A source at one of Apple's retail stores in London told Gizmodo that they are seeing "well above average" complaints and returns due to the issue.
Hopefully the Wi-Fi issues are something that can be address with a software update. Apple has already released the first beta of OS X 10.8.5 which has Wi-Fi as a focus area.