Hi Julien - I agree, and that is my experience as well so a valid improvement over the GF1.To my eyes the GX1/G3 RAWs are about 2 stops better than the GF1's at high ISO. Still I'd be very very suprised if this was shot at 6400, which is almost unusable on those cameras IMHO (even with NR).
I know how you feel, it took me a while to be convinced to part with my GF1 and get the GX1 but I have to say in hindsight it was/is for me a worthy move.Very compelling Ian, and I'd look forward to some +1600 samples too to really convince me to upgrade from the GF1
What I have noticed in my recent comparisons, and would love to be proved wrong here, are the two cameras capability at base ISO. So far from what I have seen the ISO100 files from the old GF1 sensor seem cleaner than those from the GX1/G3 at ISO 160. Not meaning to come across as contrary but realise that I shoot more at base ISO than anything else.