I own the G1 and LOVE it. And while I was intrigued with the GF1 I realize I would definitely want the EVF (or some finder) that's available (for an additional $200) and that would, as Reichmann of the Luminous Landscape put it, bring the profile of the GF1 closer to the G1 (which when I saw it originally was instantly sold on it because I realized it was about the same size as the M8 or M9).
Plus, the attached EVF doesn't hold a candle to the one in the G1 in terms of clarity and information. And manually focusing optics (like many folks use on M lenses or the luscious Zuikos I've read about or even the Leica 14-50mm f2.8 for the 4/3s to great success) via the adapter with the G1 EVF would be far more accurate than through the add-on for the GF1. And with some of these lenses you need all the help you can get.
Also, not that it's a deal breaker, I like the the articulating LCD on the G1 which can either be swung out (which I've found handy on low level shots) or reversed to remain totally hidden (and off to save power). A feature you forfeit on the GF1.
What's more, I realized with the 20mm f1.7 pancake lens (which you can buy separately), the profile of the G1 would still be really quite small and reasonably unobtrusive. (Again vs the digital M's and most certainly vs ANY DSLR). And when you consider the G1's relatively muted shutter, about as quiet as the digital M's.
Finally, I wonder whether larger lenses on the GF1 would make the unit as a whole a little unwieldy.
So what's the appeal of the GF1 other than a slightly larger and more sophisticated point and shoot?
(The LX3 with its 24mm - 70mm f2.0 (equiv in 35mm speak) lens and ITS optical finder seems like a better back up still.)
Would love to hear some of your thoughts.