I am having this issue on my Apple devices as well, the new update unfortunately has not improved things for me. Especially the iPad 3's performance is really terrible since upgrading from iOS 7 to any of the iOS 8 versions. Said iPad was still running really smooth before the updates (with the exception of a couple of more demanding games), now it is a pain to use it at all. Performance on my new iPad Air 2 is better but not nearly as smooth as iOS once was.
I was going keep the iPad 3 because of its cellular feature (got the new one wifi only), but the way things are at the moment it won't be of much use to me. If only we were allowed to go back to iOS 7...
Performance of my iPhone 5s also decreased since upgrading, but since I'm not using it as much as my iPads I don't suffer as badly using it;-)
Maybe it is time to get back on my old iPhone 4, which still runs an older iOS;-) But seriously, this glitch totally ruins the Apple experience I am used to, and while I understand that some bugs are difficult to fix quickly, it would be nice to be given a chance to "downgrade" for the time being, especially our "older" devices...