The one factor that most likely attributed to the lack of finesse of the iOS 8 upgrade is that the number of iOS 8 "developers" is exponentially higher than that of iOS 7. There was a breakdown somewhere that I'll have to look for, but the approximate proportion of actual developers on iOS 7 was about 1 to 7 or 1 to 8. The approximate proportion of actual developers on iOS 8 was something around 1 to 12 or 1 to 13. Meaning for every 12-13 claimed developers, only 1 is an actual developer that's testing/troubleshooting/using the beta iOS for testing/developmental purposes. The latter 11-12 supposed developers simply purchased a UDID registration off of eBay or some other source to gain beta access.
Because of the lack of reports filed towards Apple to report bugs and issues during the beta phase, the GM release of iOS is continuously deteriorating with every iOS threshold that's being released. To exemplify, if you look at iOS 6, it was pretty ironed out on iOS 6.0.1 for testable devices (iPhone 5 wasn't released, so you can't exactly test it publicly). iOS 7 took a bit more time in needing a 7.0.6 update to iron out the bugs. iOS 8 at 8.1 is still nowhere near as refined as 7.0.6 of mechanical issues such as touchscreen lag/latency, etc.
TL;DR: iOS GMs pretty much sucks more and more with every subsequent release from lack of actual testing.
Because of the lack of reports filed towards Apple to report bugs and issues during the beta phase, the GM release of iOS is continuously deteriorating with every iOS threshold that's being released. To exemplify, if you look at iOS 6, it was pretty ironed out on iOS 6.0.1 for testable devices (iPhone 5 wasn't released, so you can't exactly test it publicly). iOS 7 took a bit more time in needing a 7.0.6 update to iron out the bugs. iOS 8 at 8.1 is still nowhere near as refined as 7.0.6 of mechanical issues such as touchscreen lag/latency, etc.
TL;DR: iOS GMs pretty much sucks more and more with every subsequent release from lack of actual testing.