Folks, we all have pretty much the same issue. It has nothing to do with signal strength as it happen even if the ipad is seating on the router. It has nothing to do with a particular unit, as it happen after replacing my ipad2 twice.
It happends to all ipad2 I tried and with all IOS I tried. Nothing that was suggested here helps. I tried all of it, including the cover (good thought), and just about everything except changing to static ip service or removing the password, which I am not willing to do. I believe all the solutions offered here seemed to work at first since it is an intermittent issue, so people get excited and post about it, but forget to post later when the issue returns...
Perhaps the issue is with only certain routers? Mine is Netgear wireless N 150 WNR1000. I suspect the issue does not happen in all routers and when not using encription, otherwise we would have heared more complains about it. Maybe it is not noticeable on units with 3G. I tried tethering to my iphone hot spot and so far I did not notice this issue, so I suspect there are no issues when using Apple products such as the $100+ airport.
Basically the ipad2 looses wifi connectivity every minute or so, and regain connectivity only under certain conditions, which I am still not sure what. One thing I noticed that during very long downloads which requires constant connectivity such as downloading HD movies, it does not loose connectivity. It only loose connectivity when it is idling for a moment. As such, it is most likely a simple software glitch in the ipad2 that every college grad could fix in few days. What I don't get is how we let Apple get away with it. Even with a major new iOS they could not provide a fix? There is so much noise on silly issues like battery life and antena problems on iphone 4 yet such a major issue with ipad goes relatively quiet? Why we don't hear about it in the news? How come I can walk to an Apple store and someone who calls himself genious is telling me that this is probably a problem with my ipad since ipad should not have wifi issues, and is willing to replace my ipad, wasting my time and causing Apple to loose money? How arrogant or stupid can Apple be to ignore or not beeing able to address this issue?