While the performance is very good, doesn't hit 30 average so I don't see it worth an upgrade over the 285 either. In my experience you need 30 average for a smooth Crysis experience. Better to wait it out and see if Nvidia's next top single GPU solution can hit 30.
Intel_Hydralisk: If you still have a 8800GT, then I'd say this card is worth it.
Dude,look at the minimum fps.Very high settings vs high/normal on GTX285 and 4890
http://www.hardocp.com/article/2009/09/22/amds_ati_radeon_hd_5870_video_card_review/8