recent poll, a sizable number of folks have had problems with their iPad losing its WiFi connection, and Apple has now confirmed that such an issue does exist -- although it's not exactly saying there's any problems with the iPad itself. According to a new knowledge base article, the issue is known to occur with some third-party dual-band WiFI routers, and tends to happen if you're the same name for each network or different security settings for each network. To ensure your iPad automatically rejoins WiFi networks, Apple suggests (you guessed it) giving the networks different names, and making sure that they're using the same security settings. Of course, that doesn't explain why other devices are able to work just fine with said routers, but this looks to be the most we'll get out of Apple for the time being.
P.S. At least some users have also reported some success in fixing the issue by simply turning up the brightness on their iPad (of all things), but Apple doesn't seem to be recommending that as a solution.