Leica lens on GF1 - User experience?

I noticed there are a lot of people taken picture with GF1 and Leica lens combo. How do you like it?

I saw this 40mm 1.4 Leica sold for $400 which made me thinking (I can own a piece of Leica for $400, really?)

http://www.adorama.com/VT4014.html

I assume you need an adapter for Leica lens, and sacrify all the AF feature, right? Can you focus manually with the small eViewfinder?