Following in the steps of Jono's K5 vs M9 comparison, I thought I'd share an informal comparison of K5 and GH2.
The size comparison is a bit unfair since the Leica is a 1:1 macro.
I purposely chose a high DR scene, but this is not a rigorously controlled comparison. I used manual exposure to try to get a similar exposure with both cameras at base ISO. K-5 had 70/2.4 mounted, and GH2 had 45/2.8 mounted. I tried for similar framing but still ended up framing the GH2 shot a bit wider than the K-5. Both were at f/7.1 (GH2 lens a bit more affected by diffraction at this f-stop). I did use a tripod, self-timer, and kept image stabilization off. Both files were processed from RAW in Lightroom 3 with default settings.
Resized images, Pentax first:
Full-res conversions, Pentax first: