I compared a HTC Desire (same screen with the nexus) with a 3GS side by side. While colors 'pop' more on the desire, they seem to me rather artificial and cartoonish in photos (faces).

Text chars margins are slightly irregular under a magnifier lens, but the higher resolution compensates. It becomes obvious when compared with my HD2 (same res) though, so I guess it will look crappy next to the 4G.