I haven't tried the 50mm f1.7, but I have tried the 50mm f1.4 on my G1 with an inexpensive fotodiox adapter. I was blown away by how sharp the lens was when I made a few test shots. Blown away.
Unfortunately, I haven't had a chance to try it out other than testing it a little bit.
I got mine out of a grab bag of an SRT-202 kit. Along with the 202 body, I got this 50mm f1.4, a vivitar series 1 28mm f1.9 and a vivitar series 1 70-200 f3.5. The 28mm was interesting. It wasn't very sharp, and it had this weird look. I hope to use it for the lomo-ish effect it has. The 70-200 I haven't tried much with yet. I checked it out quickly with a couple of shots inside, but it was really too dark at the time to handhold it. I plan to try it out outside when I have a chance.
Total price for everything : $55 shipped. (not including the mft adapter)