I got my HTC 8x yesterday. It took a loooooong time to charge, like 6 hours. Battery life went down from 99% to 70% in two hours of heavy use. But now it is sitting next to me in idle, and holding at 60%. I think it'll improve. I have been following the suggestions here. I will not return this phone. It is too awesome!
Somewhere in a forum I saw an 'official' HTC battery calibration procedure. It said to keep charging the phone over and over with restarts in between (leaving it on the charger) until the LED was green at restart. I tried that with mine but gave up after four restarts.
I figure it's SOP for the phone; my wife's Lumia 521 stays at 100% for a couple of hours before it drops.