If you look carefully at all the reviews out the 470 often beats the 5850 in averages and even more often in mins, particularly with AA on.
IMO it's a perfect 1920x1200 card. It also seems to respond well to overclocking.
These cards are going to be more popular once they've been out a while and users have been overclocking them. If the 470 isn't enough for you, you could always grab another for SLi.
Some folks might be interested in nVidia 3d vision too. That can currently be done on Alienware OptX AW2310 3D monitors, and ACER GD245HQ and GD235HZ monitors. You need the glasses/kit too. I was very
skeptical about nVidia's 3d vision until I tried it on my neighbor's Alienware LCD. Now I'm getting a 470, the kit and an ACER GD235HZ to run it myself on my second rig. Supported games below.
5850 Crossfire is a great value and something to consider. IMO you wouldn't go wrong with any of these cards or combinations, pick what you prefer.