The only major problem I've had with WiFi is that I had to re-enable SSID-broadcast on my Router. I had it turned off, and even when I manually entered my SSID, the Droid just refused to connect to it.
Re-enabled SSID, rebooted the Droid, let it find the connection itself, entered my WPA2/PSK key (LONG key there!) and it's been perfect ever since. This was on Nov. 7th or 8th, a day or two after I got the Droid.
Oddly enough, my network shows up twice in the list of networks available -- once as unsecured, not in range; and once as WPA2-secured, in range. But it always automatically connects to the secured, in-range one... I haven't messed with it at all (trying to remove the unsecured out-of-range listing of my network, for example) because I'm afraid to mess up WiFi on my Droid. After reading about all the WiFi problems out there, I'm not going to risk being locked out of my home WiFi network by making changes -- it works now, so I'm not messing with it!