If this thing will OC close to GTX 580 speeds then this is a nice deal.
Alot of the reviewers have fried their cards, due to driver issues and slight overclocking on them.
Only reason, Im writeing a responce is just so you dont assume you ll get the 590 running like stock 580 speeds, because you most likely wont, and would end up killing your card if you tried.
Youtube video of a 590 pulling abit to much power (720$ down the drain):
http://www.youtube.com/watch?v=sRo-1VFMcbc&feature=player_embedded
If you keep it around stock your probably safe with them though.
looks like (from just looking at Anandtechs review);
performance 6990 > 590
coolest running 6990 > 590
lowest noise 590 > 6990 (590 oc vs 6990 oc, is 63 dB vs 65 dB when playing crysis)
lowest power use 6990 > 590
best OCer 6990 > 590
price 6990 > 590