I just noticed this issue this morning before i left for work, Last night before i went to bed i left the WiFi on....of course my ipad went to sleep on its own and when i woke up this morning i turned on my ipad and no wifi. Shortly after unlocking the iPAD the WiFi came back on. Updated my iPad to IOS 6 on Saturday (surprised i hadnt noticed this before now), and i updated my phone one day last week. This issue is happening on both my phone and my iPad, its happening at home at work and at the Panera Bread where i get my bagel. However, my wifes original ipad with IOS 4 is not having any issues. Her ipad went to sleep with wifi on and woke up with wifi on.
So this morning i called Apple support and explained my situation to them just like i explained it above. I got a very helpful support person named "L", after listening to my explination he put my on hold for about 5mins. When he came back he said there were a couple solutions that we could try, BUT Also, he said that apple was aware of the issue and IS WORKING ON A FIX FOR THIS PROBLEM. He said he didnt know about this problem until now, but that he tested this out on his phone and he was having the same problem He said that about 45 secons after sleep the iphone is dissconnecting from WIFI. He tested this by pinging the phones ip address while it was asleep.
So just to confirm i reiterated to L, this is a problem with IOS 6 and is affecting phones and ipads....to which he said yes. And i asked apple is working on a fix to which he said yes. He said they should roll out an updates prolly withing a week or so.
Very frustrating but atleast they are aware and they are working on a fix.