For the benefit of research and trying all lenses on all bodies I took a few pictures with the Summilux 25mm f/1.4 4/3 lens on a Panasonic GF1 with a Panasonic 4/3 > m4/3 adapter. Not a particularly pleasant experience because of the inadequacies of the Panasonic bolt-on electronic viewfinder. It really is a weak link in the whole Panasonic m4/3 range, and doesn't stand comparison with the excellent Olympus EVF. Its a shame these aren't interchangeable like the lenses. Panasonic really do need to upgrade this ASAP.
The lens performed very well, when I could focus it properly, but I doubt whether I will ever use this combination again.
However despite my serious reservations about the viewfinder, the main point of this piece is to once again say just how good I think the GF1 is. Over the past few days I have been looking again at some other alternatives, in this size range. Both the Sony Nex system and the Ricoh GXR modular camera get great reviews and praise for their image quality. However looking at a lot of raw files from those cameras I see nothing that makes me want to change my mind about the GF1.
With the right lenses, and for me these are the 14mm, 20mm and 45mm Panasonic primes, I see nothing to surpass the GF1 at low ISO's. The raw files I've seen from the Fuji X100 do seem to be pretty special but thats a fixed lens camera and doesn't have the versatility of the GF1.
Its weak links are both the previously mentioned EVF and the high ISO performance, which is pretty poor. I can get round the poor EVF for my 14mm and 20mm lenses with the Voigtlander zoom optical viewfinder I have. Though when using AF lenses the EVF works well enough for composition. Unfortunately I can't really use it for low light, except with the 20mm, which does allow it to be used indoors.
However the image quality, for what I use it for most is excellent and the camera is very nice to use. I've tried all the Olympus Pens, and prefer it to them, its better quality than the Samsung NX100, though I do like using that camera, and as mentioned previously theres nothing from the Ricoh or Sony systems that makes them an alternative to the way I work.
I hope that Panasonic haven't abandoned this size of camera for the GF2 and similar. I really did find that just too small, even though it produced results almost identical to the GF1. I can only hope that the success of the Fuji X100 persuades Panasonic to try something similar. The GF1 is just the right size for me, and a version with the GH2 sensor, and a decent built-in EVF, would be ideal. It may arrive, but somehow I doubt it, so I'll probably be left with the GF1 and wondering about what might have been.