On my first day with the phone I managed to get a shocking 7 hours with heavy use tweaking things and getting to know Android. Screen on pretty much the whole time with a combination of 4G and WiFi running too. I was absolutely floored because my Pre would've been dead in half that time.
I've followed the "20 steps" list posted here along with some other suggestions from the board and don't use Bluetooth, which pretty much covers battery saving steps...no underclocking yet.
When I'm not using the phone, I seem to be losing 3 or 4 percent per hour. When I am using it, it seems to be around 12-15 percent per hour if my tests yesterday were any indication.
I'm guessing my day one experience was a fluke, but I'm definitely not complaining. Now on to day two.