I'm currently in Tokyo on business and bought a GF1 with the 20mm F1.7 and 14-45 zoom about a week ago. I also bought the 7-14 mm F4 lens a few days ago. I've been working long hours, the weather has been pretty terrible for photography, and I don't have a mounting plate to attach it to my tripod (just an L-bracket for my 5D II), so I've been unable to give it a thorough test.
Based on my limited experience so far, I'm pretty happy with it. It handles well, has a quality feel, focuses well, and the lenses seem to be of good optical quality. The smaller sensor means more depth of field than a 35mm camera, so the 20mm is more often usable wide open than an equivalent lens on the 5D II would be. Based on my few test shots so far, the 7-14 may be an outstanding lens, considerably sharper than the Canon 10-22 F3.5-4.5 or 17-40 F4 L.
On the other hand, I'm a little disappointed with the noise levels. Of course I expected it to be inferior to the 5D II, but it's a bit noisier than I had hoped, although far superior to the G10. I haven't seen the photos on anything better than my laptop display, and haven't had time to experiment in Photoshop, so I wouldn't base any conclusions on what I've seen so far.
I should include a warning that the cameras on sale in Japan have the language selection function deliberately removed from their menus, so the menus can only be displayed in Japanese. I downloaded the English language manual, which explained how to change the language, but the relevant item doesn't exist in my camera. Apparently the cameras on sale in England can support Japanese menus, so I can only assume that Panasonic deliberately crippled their Japanese market cameras to prevent foreign visitors from buying them. I was aware of this problem when I bought the camera, and can read enough Japanese not to be seriously inconvenienced by it, but I find the thinking behind it to be deeply offensive. Perhaps someone will work out a way to install foreign market firmware onto the Japanese market cameras, although I don't know if I'd want to risk it.