Picked up my Panasonic GH3 yesterday.
First impressions:
Big for a m43 body
low noise, iso 6400 is totally usable, iso3200 is smooth
ISO 12800 and 25600 are not really much use, too noisy
electronic shutter is neat, minimal blackout time with that, but limited to ISO 1600
wifi tethering and remote control seems buggy
using beta of ACR 7.3 to edit RAW files until everything else catches up
video abilities are exceptional, quality is exceptional

Looking forward to getting more use out of this bad boy...