I am having a whale of a time using my FD lens collection on a recently acquired Panasonic G2.
I bought a very nice adapter from ceico7 in Poland on eBay.
I think the kit Panasonic 14-42 lens has been on the camera about twice since an FD adapter arrived in the post. I'm enjoying it as much as using my A-1.
Pop the G2 into Aperture priority mode and it handles the exposure stopped down with stopped down metering, but the EVF compensates well for the reduced brightness all the way up to f/11. Beyond that it gets a little dicey, but diffraction is really visible anyhow. I reckon I nail the focus about 95% of the time without needing to check with magnified view. If you do, you can be sure it's spot on. Probably as good as my hit rate with a split image screen on one of my film bodies.
Some examples:
http://www.flickr.com/search/?w=74891768@N00&q=panasonic g2 fd
http://www.skyscrapercity.com/showpost.php?p=77731997&postcount=10537
http://www.talkphotography.co.uk/forums/showpost.php?p=3662527&postcount=6
Pretty much everything here since 4th May
http://www.cybertects.co.uk/gallery2/v/architecture/london/shard
The results mostly bear out my experience with them on film with odd exceptions.
Primes: The FDn 50mm f/1.4 is wonderful, I'm very pleased with the FDn 135mm f/2.8. Plenty of blur available even with a crop.
28mm f/2.8 and 35mm f/2.8 aren't quite in the same league but perform well enough stopped down a bit.
The FDn 17mm f/4 has been a bit of a disappointment at the edges, but it's a useful focal length on a 2x crop.
Zooms: FDn 35-70mm f/3.5-5.6 is OK but not great. The 70-210mm f/4 has proven surprisingly good (with occasional unaccountable moments of softness).
I've yet to try out a my breechlock FD and FDn 50mm f/1.8s and an FL 50mm f/1.8 on the G2, but that's mostly because the f/1.4 has proven so good.
Currently investigating the purchase of a FD 24mm f/2.0 as that would give me a good approximation of a standard 50mm on full frame. I'd be tempted by a 20mm f/2.8, but I think I'll save my pennies for the Panasonic 20mm f/1.7 pancake for street photography and maximum compactness, especially at the prices the Canon 20mm is going for these days.