The E-P1's performance is good for a compact, but looks a little slow compared to most DSLRs. It starts up in well under two seconds, although if you're using the 14-42mm lens you have to remember to manually extend it from its folded position first. In single shot mode the slow autofocus means that is has a shot-to-shot time of approximately 2.3 seconds. In continuous mode it shows how fast it could go, by maintaining three frames a second in both Raw and JPEG modes.
I haven't had a chance to try the 17mm f/2.8 lens yet, but the Zuiko 14-42mm f/3.5-5.6 lens is excellent, producing pin-sharp detail from corner to corner at all focal lengths with barely any optical distortion and no trace of chromatic aberration thanks to the use of ED glass. There are two optional adaptors available that allow the E-P1 to use both existing E-system lenses and even OM-system 35mm lenses. As far as I know it should also accept Panasonic G-system lenses.
In terms of overall image quality the E-P1 is a bit of a mixed bag. Exposure metering is up to Olympus's traditional high standard, and in good light the results are excellent. In high-contrast conditions it has more dynamic range than any compact I can think of, with detail even in dark shadows, although even in Raw mode it blows out some highlights that a good APS-C DSLR would catch. Colour rendition is also very good, with plenty of detail even in bright saturated areas.
I was expecting the E-P1 to show similar high-ISO noise results as the Panasonic G1, but unfortunately this is not the case. While the G1 doesn't start showing any noise until 800 ISO, the E-P1 has visible colour mottling and noise in the darker tones at its default auto setting of 200 ISO, getting progressively worse, although overall colour reproduction remains reasonably good right up to 3200 ISO. JPEG images also show some over-sharpening, but at least the compression rate is nice and low, with fine JPEG mode producing files of around 5.5MB and Raw files of around 12MB.
The Olympus E-P1 is an interesting and innovative camera, and as a first model in what will probably be a series it has some very nice features. Build quality and finish are of an exceptionally high standard, and image quality and performance are safely superior to the vast majority of compact cameras. However the enormous cost compared to a good DSLR, and the lack of either a viewfinder or built-in flash will put many people off.