I'm surprised nobody has suggested the panasonic 20mm f/1.7 (40mm equiv on the 2x crop of the GF1). In a similar fashion to the 50mm f1.4, I find the 20mm to be one of the best lenses you can buy at a reasonable price. Not to mention you'd get the benefit of having AF since it's a Panny m43 lens on a panny m43 body. Did I mention that the lens is TINY and is a fantastic match with the GF1 body?
I have the canon 50mm f1.4, and on my crop sensor body - I found it a bit too long for my taste. At 80mm, I found myself having to step back alot to get the FOV I was looking for. It's perfect on the a full frame body though.
That said - I also have the 20mm f1.7 on my GF1 and it is a fantastic lens with excellent IQ. The bokeh is nice at f1.7, but due to the smaller sensor size and obvious being a bit slower than f1.4, the DOF won't be as shallow as something from and APS-C size sensor - even if both were at f1.4. It's just the nature of the beast.
From someone that owns a 50mm f1.4, I think you won't be disappointed going with the 20mm f1.7 panny lens