Nvidia 6800GT. Without question.
Solid drivers.
Great OpenGL performance (think Doom3 and ALL the games in the future using id's engine).
Full 16 pipe card.
Single Slot/Molex
Quiet
Easy overclocks to Ultra, which puts you in the same ballpark as the X800XT-PE.
SM3 (which might mean something one day! :-))
Have one myself. Very happy with it after one solid weeks worth of testing on 10 games. It's the PNY, which PCW now list for only 226+VAT, which includes FarCry and Splinter Cell. Damn good deal,
imho.
Reviews? Jeez, do a bit of searching. The web is full of them (Tom's, Anands, HardOCP, TechReport, and every other hardware site you can think of - try googling).
Nomadd