I plugged in my 2900Pro 2 weeks ago and it did look a bit more vibrant on the desktop and games but as I was already thinking about people's vibrancy differences between ATI and Nvidia so I can't be certain if that influenced me?.
It does seem to be the common consensus that ATi cards produce a more colourful/vibrant image, though I can't say if I've seen it myself since I don't have anything to compare to my current setup. One thing I did notice though was an option within catalyst colour settings that when turned off turned the image grey/washed out in comparison, maybe that's the difference?