I have this issue also - I notice this when streaming SD or HD videos from my NAS, or reading comics/ pdfs via streaming from my NAS.Wi-Fi connection is totally slow. Maximum speed is 0.5 to 1Mbs. Other devices on the network works on full speed (5Mbs).
On TNT4 wi-fi worked normally on full speed.
It connects ok bu performance - wow I nearly wanted to throw the dmn thing.
Also, since iwconfig an iwlist is included, I was able to determin that the wifi chipset can only report max rate of 65mbps - way off standard N rate of 150
I was RIGHT next to the router when i checked.
IS this an issue with previous release or inherent in the hardware already?
I will try to restore v5 to see when i am able to.