There is a GH1 vs G1 RAW comparison thread inside the dpreview forum.Klick on picture to see it at normal size.
This comparison is made at ISO3200, equal exposure for both, sharpening and NR turned off and developed with RawTherapee.
The people inside the forum have different opinions, some believes the GH1 is clearly better some other believes the difference is minimal. At first look it seems the banding issue at high ISO is still here (it looks slightly different between the two cameras). And may the G1 still looks a little sharper?