I upgraded to Windows 8.1 and Wifi worked fine - UNTIL I followed the advice of the little balloon in the lower right to upgrade my Intel wireless drivers. Clicking the balloon led to a page on Intel which had a driver for 32-bit windows. I blindly tried that, but it wouldn't install and instead I got the message to use the driver for 64-bit windows. OK, so I downloaded that and when I tried to run it I got an Intel icon and then it quit.
That driver wasn't the latest anyway, I discovered today via a Google search. So I downloaded version 17.0.1405.02. That installed, and at the moment I'm able to reach the Internet quickly without even restarting Windows. Let's hope this continues...