Apple seriously hosed the 8.XX releases. I have an iPad 4 that worked wonderfully on 7.1.2. My "upgrades" to 8.0 and 8.02 have cut my wifi speeds less than half and app performance is very sluggish. There are some web pages that I can't even load anymore. Safari is close to useless (Chrome and Dolphin work a little better). I use my iPad partly for work, so this horrible performance has been very painful.
I've tried downgrading back to 8.0, but it has only helped slightly with fewer app crashes than 8.02. I've tried restoring, resetting network settings, restoring all settings, downgrading the firmware using DFU mode, turning airplane mode off/on, turning airdrop off/on. I did a full factory reset to both 8.0 and 8.02 and wifi was still ridiculously slow. I have two very different routers (NetGear Nighthawk and Apple TimeCapsule) -- the wifi performance is roughly the same on both. Although I have slightly fewer outright drops on the Apple router, it is still painfully slow. Also, running Speedtest isn't actually a good test - at least for me. I can test the upload/download and the problem seems fixed, but as soon as I try to navigate to a web page in Safari or even open Mail, speeds are very very slow.
Apple -- please, please, please start signing 7.1.2 again.