I did an examination myself with dcraw of someone at dpreview (rickyastro? I forgot), that kindly posted shots in same ballpark conditions of the GH2 and the EM5.HI Bart
The review is interesting - they seem to think that the dynamic range is better than the G3 . . . and the RAW high ISO looks better as well.
I've ordered the kit lens - the grips come free (which was why I cracked and ordered it today).
My analysis puts the highlight DR at slightly over 1 stop and shadow dr at a notch better than the GH2! Therefore it is indeed better than the G3/GX1 by a noticeable margin because the GH2 by reference to the others, scores best in DR (Dxo). In fact the GH2 was the best 4/3rds/ m4/3rds DR until now.
This also made me change what I thought was at first a tweaked GX1 sensor (and if it's a tweak it's a hell of a hardware tweak!). For some reason early images that came out didn't show this kind of performance. I wonder how many "reviews" had in their hands pre-release/beta cameras and not final product.
Really happy for Olympus here and glad they were able to put a nice sensor on a new camera. I don't know why people find the price expensive. Even with the GX1 sensor, I would have found the price fair for the whole package. I think the price is quite adequate, very much unlike what happened when the E-5 was released.
At this point I am thinking a bit about it as a way to consolidate using two cameras (Q and K-5), but not sure yet. I like the Q and K-5 a lot, but having two instead of one is something that I think gets in the way of focus- for me. Maybe I'll learn to really live with that. On the other hand the EM-5 doesn't get me pocket ability but I think if at least I could put it away in a pocket without a lens I could deal. I just want an option of "putting away the camera" and be able to "wear it" while forgetting about it.