wonder if you have a bad battery.
I got a loaner from CPS, and took it along a snowshoeing hike yesterday. I had it powered on the whole time, exposed to single digit temperatures - wind chill driven, and powdery snow. The is on the mounted 24-105 was on too.
Took 100 shots or so, and even after checking all the shots later in the comfort of a local bar, the charge was still above 85%
I find the grip ergonomics better than the 1dsmk3 or the 5Dmk2 with grip
Yes, the shutter it's a loud and solid clunk - and 12 fps scares nearby P&S shooters