I expect to like it more when my 7+ arrives so that all the advertised features work, but for now on the iPhone 6 I am mostly unimpressed.
-The new unlock feature does not work reliably, occasionally causing the phone to open the Home screen when I am merely resting my thumb on the TouchID sensor with the expectation that it will just unlock the notifications screen.
-Control Center does not return you to the 1st panel but instead remains on the last panel visited making it take longer to use the flashlight or turn Wi-Fi on/off.
-Apps have been crashing, glitching, loading slowly, and showing other weird problems. This includes Apple's built-in apps which have been unstable. Power-cycling the phone has not resolved this so I expect I will need to wipe and restore the phone if it's a corruption issue.
-Downloads have been abysmally slow, especially App updates from Apple's servers. Could be due to so many people updating to the new iOS at the same time, but annoying none the less.
Things I like:
+The new unlock screen is great when it actually works
+HomeKit control from the Control Center works instantaneously, faster and more reliably than the OEM apps do
+Finally able to remove crapware from Apple
Things I look forward to once I get the 7+:
+Raise to wake
+Hopefully, a more reliable unlock screen experience
+3D touch
+Untethered "Hey, Siri"