NEX = piss poor UI and inconvenient to an extreme if you want to shoot in anything but auto-everything mode. It does come in cute fashionable colors, though...I mean, if you need something to match your shoes or handbag.
Same goes for the Oly PL-1.
The GF-1, E-P1, & E-P2 have a much better control layout and quick access to all modes and control in those modes. Being m4/3 also means a good selection of native lenses as well as being adaptable to more mounts then any other mount type. Also, the 4/3 standard includes things like the flash communication protocol, so Oly flashes will work fully TTL on Pana and vice versa. I'm using a Nissin Di466.
I'm guessing that you are considering the GF-1 because it seems to be the flavor of the week, but I've played with a GF-1, E-P1, and E-P2 and can tell you that the PENS are better buys. Here's why:
Better image processing (albeit a non-issue if you're shooting straight RAW)
In-Camera IS (works with manual focus lenses, too...AND when recording video in the E-P2)
Full Manual in Video mode on the E-P2
Better pixel density (3x) on the E-P2 EVF
I agree that the Pana 20/1.7 is a great lens. Thankfully, you can use it on the PENS. And with the current firmware, the E-P2 with the Pana 20/1.7 focuses slightly faster then the GF-1.
I currently own an E-P1 and E-P2. After lending the E-P1 to a friend for a couple of weeks, he asking to buy it from me and get rid of his GF-1. The in-body IS combined with the 20/1.7 makes for a great low-light combo.