Maybe your wifi is broken; but I have no way of telling if it's a hardware problem, a firmware problem, or a wireless network problem. I do suspect that something in the firmware is having trouble with some specific wireless network configurations. Unlike some folks, I cannot magically diagnose problems over the internet and I have not seen any obvious common factors in the networks that are having problems. This leads me to believe that the problem only occurs under some specific network conditions (routers, channels, other devices, etc.).
My 3GS, 3G, and ipod touch are all working perfectly with 3.0, so if it is a firmware problem it certainly isn't affecting everyone. I will be curious to see if the actual solution is similar to all the speculation.
According to my calculations, a few hundred (or a few thousand) is a very small percentage of a few million; but I do understand that it's frustrating when you are being affected.