The PB WiFi quality is ultra uneven. Mine always shows low signal, compared to two other PBs that I have got for my relatives. My PB has to be 3 ft away from the router whereas my two laptops and iPad have absolutely no problem connecting 20ft away.
As PB fan, I hate to say this but there is a reason why RIM is not doing well if they can't even get something as basic as Wi-Fi working.