GH1 or GH2?
I can't really add much to what Button Pusher has already said, but I upgraded from the GH1 to the GH2 in October. I've found colour rendition to be better with the GH2, and despite what DxO might say about dynamic range being better with the GH1, I've been able to pull back some great detail out of dark areas with the GH2.
The touch focus is a wonderful addition, allowing you to manually select the focal point without having to scroll across using the directional buttons. Just tap, and that's your focus. Brilliant.