I am also having this issue. Before GB, my WiFi would disconnect all the time, even though I had the settings set to never disconnect. That was annoying.
Now it seems that the WiFi does disconnect, but less frequently. However, the connection remains but it just stops working. This morning I was browsing the internet, and every 5 minutes a page would not load because the connection was lost. I would have toggle WiFi off and on again and wait for it to reconnect and it would work again. This makes my phone almost unusable.
I do not have Juice Defender, I do not have data saver setting turned on, I have WiFi set to never turn off. And I've rebooted. And I'm rooted.