It's just as I feared. They are not as good as I thought they'd be. This is however, excellent news if you're anything like me. I think I might get the 5xxx or even 4xxx generation cards now that the release of the new 6xxx generation cards has lowered costs. They compete, but I win! It will come down to price for me, and I feel like I can't lose here because the 6xxx will still scale better for future crossfire setups.
As for how it compares to a gtx580 I could care less because I have an AMD board and SLI doesn't scale as good anyways. Hopefully the 6990 will come out soon and drop the prices of previous generations(that I want more at this point) just a little more also. This is excellent news and I plan to take full advantage of the price drops.
Edit: Also, I really wouldn't judge ati vs nvidia's latest batch until amd/radeon releases their best offering- the 6990. Nvidia already released their best, and while they are most likely the king of single gpu cards, i'm predicting a repeat of the gtx480 vs hd5970. Nvidia has good drivers, engines, and a few stats they accel at; but amd will inevitably have more stuff they are faster at as well as have multi gpu support. Plus I mean, what are you gonna do? If you have an amd motherboard and want to eventually have multiple cards you are stuck with amd/radeon/ati cards. Wait for the final series to come out before fully forming an opinion, is the point i'm trying to make here.