IQ, DR, lens sharpness corner to corner, the way the foveon sensor draws makes it unique and its output can stand up against any camera.
Among the compact digitals, the DP1's IQ is still in a class of its own.
As others here in the forum, I tried literally all of the more recent top of the line small sensor cameras (G9, D-Lux3, GX100, GRDII) and resold them soon, simply because of unsatisfactory IQ (and DR). UI wise the DP1 will grow on you. Main issues are the sluggish AF and the slow file write time. However, in MF and zone focusing mode, it is a pretty snappy camera, good for street shooting, one shot at a time with 3-4 seconds wait time inbetween shots, though.