Hey Martin, I recently got the GF1 and I am totally loving it. The image quality to me, at low ISO, for what I do, is great, same a my D300. That said, I get great image quality from my Canon S90 too (although no depth of field). The difference for me is performance, the GF1 just can't keep up with the speed (frames per second, autofocus, etc.) of the D300 or higher end cameras. But the images are great. I hope the GF2 will be faster... and ISO performance improves, although with NR algorithms these days, it’s less important to me.
What I like about the GF1 is that it lets me be free to just take pictures. It's small enough that I take it lots of places, and pick it up a lot. My D300 gets left behind a lot. It's just too big and carry around, esp. with those big lenses. I have the 14-24 for the Nikon and the 7-14 for the GF1, wow, what a difference (and NOT in quality, but size/weight). And the video on the GF1 is pretty awesome too.
I don't have it underwater yet, but others have.
So, that's the format I am excited about, not necessarily the LUMIX or even m4/3, but EVIL in general. Excited to see what Nikon comes out with. I am done with the big heavy equipment that takes up lots of space in my bags…
Good luck!
Mike