My wife's ipad and my ipad2 both have issues with wifi but ONLY when using my iphone 4 as a hotspot. I turn on the hotspot initially and then get the ipads connected and all is well. But if the ipad/ipad2 are "closed" (via smart cover, timeout, or power button) and then awakened, it can't find the iphone hotspot again. The ONLY solution I have found is to awaken my iphone and go to the personal hotspot screen and then go into settings on the ipads and turn off and on the wifi to pick it up. Sometimes I even have to turn off and on the personal hotspot.
No issues with any land-based wifi connections on either ipad.