There are many internet forums with thousands of users scratching their heads, wondering if the reason their WiFi performance is severely degraded on iOS 8 is because of their router, their DNS settings (please help these folks the most), that they need to reset their network settings, and more.
I’ve narrowed down the issue to the use of Apple’s Wireless Direct Link (AWDL) that is used for AirDrop, AirPlay, and Gaming connections.
I’ll go out on a limb and say the WiFi issues are because of Apple’s choice of using Bonjour over AWDL and that, given the constraints of the WiFi hardware, this will be difficult to get right. But perhaps I’m crazy, and this is just a bug that can be fixed by Apple.
A long read, but worth the time.