Being asked to judge the image quality of what is probably the best digital camera (except for the 6 million pixel 560 and the as-yet-released DCS 600 series) on the market is probably a fruiteless effort. Ask me for a personal opinion and I'll say that this camera takes images of a quality difficult to distinguish from scanned 35mm slides (and in many cases much better).
Combining Canon's excellent EOS-1 with Kodak's obvious digital photography expertise and that wonderful 3:2 2 million pixel CCD (plus all the other clever features of this camera which we just don't get to see; or worry about) means that you'll be taking photographs with this camera way and above anything previously experienced.
Colour balance, resolution, "picture depth" (something I can't explain technically), neutrality of tones and image purity (lack of noise) are exceptional, truely a reference camera.
This camera also has the ability to cover the spectrum of "film speeds" from ISO 200 landscape, portrait and studio work up to ISO 800 fast action sports coverage.
The only criticism I could find was the occasional poor sensitivty of the camera to the colour blue, this becomes apparant at higher ISO's (and especially in low light). The images below were taken under the same lighting conditions and a PowerShot Pro 70 sample is shown for references purposes. (Poor lighting was used deliberately to highlight the problem).
Finally a side by side comparison using the Canon 380EX Speedlight:
Original sample images: