When compared to GeForce GTX 295, its performance ranges between 25 percent (25% slower) to 95 percent (almost 2x faster), another broad range. 
Sources:
http://forum.beyond3d.com/showpost.php?p=1334677&postcount=2969
http://www.czechgamer.com/novinky/5055/ATI-Radeon-HD-5870-prvni-benchmarky-jsou-venku.html

Sources:
http://forum.beyond3d.com/showpost.php?p=1334677&postcount=2969
http://www.czechgamer.com/novinky/5055/ATI-Radeon-HD-5870-prvni-benchmarky-jsou-venku.html





Tnx for the info
nVidia bl00d suckers..!!
what abt you...