"Actually, there are several verified reports of some routers which require firmware changes to work properly with the 802.11 feature set now being used by iOS 6. These are consumer-grade routers and you would not likely encounter these problems with public access points.
Of course, a lot of suggestions on this thread don't make much sense, but to ignore router problems/misconfigurations/firmware bugs is certainly a poor trouble-shooting technique."
I agree on with you troubleshooting of these devices is very important.This is part of my job.I tried every way to understand the problem.(channel mismatch, b/g/n incompatibilty, firmware, MTU, wireless band 2.4-5ghz etc...).Finally I understood that it is not one of the problem that you can solve by yourself.That's why I can say "dont try to find a solution"
I am very aware of all kind of troubleshooting techniques.I use them in real enviroment for hundreds of different devices.(cisco, hp, aruba, d-link, juniper, huawei.....) It doesn't matter If it can be fixed for some devices with firmware upgrade or changing router/access point configurations.It may work for some router/access point brands (I dont beleive that it fixes the problem permanently).If you would call something as "solution" it must work for all kind of environments.Otherwise, I call it as "misleading the people about the problem."
Ipad 3rd generation with ios 6.0.1 has a vendor based problem.This is a fact!.Instead of searching weird solutions we should push Apple to fix it.
By the way, I have found my solution and it fixes the problem %100 guaranteed....
I will return back it once I come back to my home (I am far away from my home) and I will buy android device which has no stupid problems like ipad.I bought it for my wife I never pay for apple.She didn't like samsung galaxy note she insisted on ipad.Now she has magnificient retina display without connecting internet.
I just wanted to warn people and transfer my experience.