My E-P1 and 20/1.7 arrived today!!
First impression: Heavy

Second impression: AF speed. Even with the E-P1 running firmware 1.0, the AF with the 20/1.7 is pretty much the same as the GF1. Updated it to firmware 1.2, and *drum roll* ... it's still pretty much the same! Which means it's plenty fine enough and all of that internet talk about the E-P1 having slow AF is thankfully largely rubbish. (At least with this lens.)
In a near-pitch-black room however, the E-P1 struggles to lock focus just like my D90 + 28-75/2.8. The GF1 would lock focus here without a problem - that I have to concede.
BUT! Image stabilisation is the reason why I switched from the GF1 to the E-P1 and the Olympus does NOT disappoint! Every single one of my photos (and I've taken almost a hundred so far) is pin-sharp. Of the first 100 of my GF1 photos (same lens, same environment), 29 showed camera shake.
There were 2 hot pixels on the sensor though - I was a bit worried but then found out that the camera has in-built pixel re-mapping. Simply told the camera to do its thing, and it found the pixels and fixed them! Unbelievable.
The E-P1 is also much much nicer to hold - the rubbery grip on the front and the larger bulge at the top right of the back surface means you don't have to hold the camera with much strength. Only downside is the camera strap which gets in the way more often than not, but if I can't get used to it I'll simply take it off.
Now to ebay off the 14-42....