I downloaded it too this morning, to my ipod touch 4th gen, had no wifi problems, turned it back on at end of day here, and yes had wifi connection problem, it would connect, take me to this wierd login page I never had to use, even earlier, then wifi signal gets off, page cannot be found??
So I rebooted it...twice and it seems fine for now.
I just got off the phone with applecare tech support agent who reported this is a know bug, it's happening like crazy, at this time apple is saying it is an error on their end, which should be fixed by tomorrow, in the meantime there are various troubleshooting tips you can do, many are on this questions answers, but even if you do nothing, she thinks it's on apples end, when they fix it, our wifi's will stay fixed even if we do nothing