All told, including install and reboot, it took between 3-4 hours yesterday. My initial observations:
* As always, an Apple OS update turned Bluetooth back on, even though I have it turned off since I don’t use any Bluetooth devices.
* WiFi seems to be a bit flaky compared to iOS7, especially in places where the signal is weaker.
* The new location services mode of allowing apps to use location services in the background is a good thing in theory, but one misbehaving app can suck the life out of your battery. I’ve disabled all of them, and will re-enable them one by one to figure out which one(s) are the culprit. (Though from past history with location services, I’m looking real skeptical at you, The Weather Channel app.)
* A small percentage of apps I’ve tried, notably games, don’t work at all or seem degraded to performance. Maybe next time, Apple could announce the upgrade a couple of months in advance so that developers could use beta versions to be ready for the rel... oh, right.
* Visually, not much is different. There’s a subtle difference in some fonts and icons, though the task switcher and notification center have definitely seen changes.
* No noticeable difference in performance on my 5S.
* Really, though, most of the above is low-impact. There will be a WiFi patch soon, I presume, and the real “oomph” of iOS 8 comes from Continuity and Extensions, the former is waiting on Yosemite and the latter has only a few examples out there so far, and none that I’ve really played with yet.
Have you tried a full cold restart? I had a few little problems after the install and restart, but they all disappeared after a cold restart. . . So far.
I’ve come across two extensions so far, one of which I know i will use every day and the other I might. I’ve been using 1Password since my default password got released into the wild in a hack of Yahoo several years ago; nearly all of my passwords are long random strings. I can now open 1Password with a fingerprint, and it’s integrated with Safari. Sweet.
I’ve also downloaded the SwiftKey keyboard, which has been quite popular on Android. It’s definitely the fastest way to type one-handed, but I don’t think it’s faster than both of my thumbs.
I also haven’t seen any noticeable performance hit on the 5S.