As a hobbyist, I tried the Nikkor 50/1.2 MF lens on the GF1.
Results are very promising from F1.4 and on. With the smallest light source, using GF1's ability to go up to 800 ISO without much problems, I think I may use this setup for street photography as well.
It works like a 100mm lens, which means I may stay far from the subject, which in some cases may be an advantage. ( although mostly not!)
Next trial will be the 35/1.4 AI-S, but from longggg ago, I remember that it's a very poor lens up to F2.8. We'll see.
Tomorrow I will try to post some street photos taken with the 50mm.