There's def a wifi issue still, here's a 27 page thread on apple support about it
https://discussions.apple.com/thread/3381610?start=390&tstart=0 and this one from Engadet in Nov still has comments updating about the issue
http://www.engadget.com/2011/11/21/thanks-to-ios-5-some-users-lose-wifi-connectivity/
And I can say my 4 and 3GS both have not had wifi since Oct release of iOS5. Unless I'm within a few feet of the router, and I've used two, DIR-655 Extreme and Linksys E4200. My neighbors 4 has had the same issue as well, as well as some others I know after upgrading to iOS5. No matter what changes I did to the routers, or frequency or band I changed, no difference.
Now the 3GS is jailbroken and old bootram with blogs saved, when I reverted back to previous OS, whad'ya know, WiFi works 100%, but running iOS5 again and it only works unless right near the routers. Even replaced the wifi ribbon cable just to see, and no difference. My GS2 on the other hand works 100% on the same networks, as well as our other devices (MBP, pc/laptops, kindle fire etc).
I even went to the Apple Store with my MBP to show the difference on the iPhone when running iOS5 vs previous OS on the stores wifi network. At the time, he said they were getting complaints about this but nothing could be done as Apple had nothing about this in their system.
Now months later Apple finally acknowledges there is an issue, yet they have no answer as to why it's happening to some and not others. I even wrote them an email explaining how reverting back to previous OS works fine with WiFi and to contact me with any other qeustions to see if we could solve this for everyone, they never did get back to me, so much for support
If you don't have the issue, be thankful, b/c it sucks