I got the E-P1 and the 20/1.7 as early as when they were available here in Germany, and to second what others already stated: It's a great combo! I have other lenses for the E-P1, but the 20/1.7 is attached to it most of the time, for several reasons.
- It's small, and makes the camera somewhat pocketable.
- It's fast - I can shoot it in difficult lighting situations and get great results.
- The focal length is the ideal compromise: not too wide, not too narrow. Good for group shots, landscapes, portraits - just about anything. Not so much architecture, though, and not for macros either.
- It's got lovely bokeh, and at f/1.7, subject seperation is possible at closer distances (e. g. with portraits). It's also got great colours and great contrast, and is incredibly sharp at any aperture setting.
- Combined with the E-P1's in-body stabilization, it's the ideal low-light lens. Go down to 1/20th of a second, and you get sharp pictures as long as your subject doesn't move.
- It looks great on the E-P1!

What has also been said already is that it pairs nicely with the VF-1 that was made for the 17mm pancake, as its framelines are quite a bit narrower than the 17mm actual field-of-view. Use the inside of the framelines for your composition, and you're spot on. I love this for when the sun's too bright to see the display, for saving power or just for the fun and retro-ness of it.
Samples galore:
http://www.efixmedia.de/photography/tag/201-7/
Anything else? Just ask!