I’m hoping you weren’t one of the people who was affected by the brief rollout of 8.0.1 this past week, but if so, 8.0.2 should fix any cellular issues you may have experienced. I updated my iPad Air from the iOS 8 GM to 8.0.2 last night and did a few practical tests. The main thing I noticed is that third-party keyboards now seem a little more stable. Fleksy and SwiftKey used to crash in iMessage or during quick replies, but that no longer seems to happen. I still have to scroll down every single time I load up iMessage though (unless I’m using Apple’s keyboard), so there are definitely still some extension bugs abound.
I also found out one disappointing thing about the iOS 8 APIs in general: third party keyboards are not allowed on the lockscreen. I’m not really sure why. I’m guessing it’s a security feature, but it does make the experience across iOS 8 feel inconsistent, since I prefer to use Fleksy most of the time, but any quick replies from the lockscreen force me to use Apple’s QuickType keyboard. I’m fine with password fields in iOS 8 requiring the stock keyboard, but I think my third-party keyboard should show up everywhere else.