The short of it is that, for right now, ATI holds the triple crown for image quality, performance-per-watt,
and framerate. So if you need these things, and you need them
right now (and you don't want to get there by merely lowering your graphics settings), the 5870 is the way to go. If you can afford to wait (or can't afford to switch), then by all means wait to see what NVIDIA releases (3xx in Q1 2010), or even whether
Larrabee is all that Intel says it will be (likely Q2 of 2010).