I like m42, and fd's are very good, but nikons are more adaptable. fd's are cheaper, I think they both give different looks, fd's warmer and nikons cooler. there are also some threads on personal view about the best lenses for video on the gh2
You can get a gauge of how the glass performs. It's a very warm look, and at 1.8 it gets very soft and a noticable glow appears on the edges, it can be used to an advantage, but is not ideal for wide open shots that need be precise.