Given that it has 50% more transistors and a 50% wider memory bus, 50% higher power consumption, 30~40% faster in only some games is pretty bad. 30~40% across the board would have been impressive. 10~15% when they have gone all out isn't.
It's still not too bad price wise compared to the inflated ($420) current price of the HD5870, since it gives 10~15% more performance for only 20% more cost, which at the high end is pretty much a bargain, but considering what it is, and how late it is, it's underwhelming, just as was predicted by certain people who everyone likes to discredit.
The fact that it loses in some tests is more surprising than the fact that it wins by 40% in some, given the difference in design approach.
Also 2560x1600 numbers would be very interesting, considering these are $400+ cards and you would think at least some of the target market would be using 30" monitors at 2560x1600.