Mines working fine.
Just curious. Those that its not working for, are you rooted?
Got my Thunderbolt and rooted it the same day, so I can't say if it was better before or not. My issue: the phone connects to wifi no problem, but after some period of inactivity the wifi stops working. The icon shows that it's still connected to the network, but attempts to browse with anything result in timeouts. Disabling/re-enabling wifi fixes the issue.
I have an older WRT54G router. I wonder if that's the problem?