Yes I know the S90 is a compact camera. Rather than go one down in the category, I decided to go one category down and buy the top camera in that category. fwiw here is a picture from the S90 and one from the Olympus E-P1
Looks like the s90 has some barrel distortion, but you expect that with a wider zoom lens. Otherwise, there's not much to differentiate them. But the picture was taken in good light.
The E-P1 has a much much larger sensor, and should be much better than the s90 in bad light. Also, you can get a nice 10mm prime for the E-P1 (20mm full frame equivalent, compared to the s90's 28 mm FFE at its widest), or a fast portrait lens, or a telephoto.
On the other hand, u4/3 lenses are often insanely overpriced (at the moment), and the s90 fits in your pocket.
http://a.img-dpreview.com/reviews/canons90/samples/comparedt... http://a.img-dpreview.com/reviews/OlympusEP1/samples/compare...