One of the best features of the Micro Four Thirds camera format is the short back focus of the lens mount because of the lack of a mirror. I currently use Nikon F, Olympus OM, Canon FD, Canon EF and Leica M rangefinder lenses on my GH2 with lens mount adapters. About any lens made can be mounted with the right adapter. There are no electrical contacts so the lenses are strickly manually mechanical. Because the GH2 has the zoom feature in the viewfinder for focusing, it helps with focus. i usually use my camera in manual exposure mode as well as I can see the changes in the viewfinder.
Why do I mention all this? Because of the Super Moon this weekend. Here are some shots taken with my all manual Nikkor ED 400mm f5.6 from eBay.