So far....
1. Battery seems better, not even close to 8.1 but, a noticeable bump in this build.
2. When getting a text, if I click the notification that shows up, it will bring me to messaging but, I end up a loading screen forever (waited only 30 seconds before backing out and going into messages directly).
3. Cortana on the Band 2 is hit or miss, most of the time it will say "Cant connect" or ask "is your phone in range" when this happens the watch is less than 2-3 feet from the phone (Bluetooth ICON on the phone and band are active too).
4. Still no way to Mute Cortana when she goes off (leaving "read texts outloud" set to always), in 8.1 we used to be able to hit the volume or power button to mute her.
5. A few apps random just close, crash maybe ?
It's still buggy but, like every Microsoft OS on release, it's not ready for prime time till the 10th update or so...
After you've had some experience please post your battery performance.
P.S. many people recommend a hard reset after installation.
The RECOMMENDED thing is to do a Hard reset and no restore. Sorry all but, losing game saves almost every other build sucks. I did it for a while and I now avoid it of possible.
As I said above, Battery IS a little better, stand buy is better but, using the phone depening on what you do can take a hit on it...