Maybe a tiny minority, but definitely a real problem
@Michael Brown -- This problem is real; I updated to iPhone 2.2.1 last week and my WiFi stopped working reliably two days ago.
Your logic is flawed, in that you say it's a small group of people, and yours is fine. Ok, but if a group of iPhones, no matter how small the number in comparison to all iPhones sold, all ended up with fried WiFI boards after the update, how can you say it's _not_ a hardware flaw? There are a lot of variables here -- maybe the people whose iPhones still work on 2.2.1 do not use the WiFi radio as much. Maybe they all are a ticking time bomb.... or, maybe it's just a few that are defective. But they are _still_ defective. If there were reports that possibly 1% of the drivers of the car that you own were finding that the steering wheels suddenly detached while driving at speeds greater than 40mph, would you laugh and say, "well, my car is fine!" That's tempting fate........
Regardless, I can't prove anything, but I know my iPhone "seemed" like it was getting hotter than it used to, just under the Apple logo on the back, after the update. I thought it was just because I was using it more. Then two days ago, Wifi suddenly dropped out. I've now had the exact same symptoms described -- works OK on low battery, works ok for a few minutes out of the freezer. Two different wireless networks. Restored 2.1, but the problem remains. iPhone 1st gen.