Averages about a 15 - 25% performance advantage over the GTX580, while consuming roughly 50W less at full load, and running cooler at the same time... that's a win-win. It's not as much of a generational performance jump as we've seen in the past, especially considering it's a new architecture and manufacturing node, but considering the focus of the GCN architecture this is still pretty impressive. It also dominates the HD6970 in practically every way.
With this release AMD has addressed many of the issues I've had with their recent GPU's. This generation is the first time in years I may seriously consider investing in a new ATI/AMD graphics card. Overall it's without question the best single GPU gaming solution you'll find on the market in Q1 2012, and it's also shaping up to be a compute performance beast.
First and foremost is compute performance. The shift to this new SIMD architecture shows that AMD's finally getting serious about GPGPU computing. GCN has been architected with compute efficiency and performance in mind. Unfortunately it's a little difficult to quantify this at the moment, as there aren't very many real world applications that run on AMD GPU's, much less take full advantage of this new architecture. But given AMD's shift in focus I'm certain this will change in the coming years. Current performance results look promising:
http://www.anandtech.com/show/5261/amd-radeon-hd-7970-review/25
Next is the cooler. AMD has finally designed a tapered, angled cooling solution with full rear ventilation. This is a far cry from the flat, totally inclosed brick on the HD6900 and 6800 series. The heatsink may have been fantastic, but without decent airflow none of that really matters. And it shows in the results, while the HD7970 consumes more power than the HD6970 at load, it still manages to run at similar temps, if not cooler.
http://www.anandtech.com/show/5261/amd-radeon-hd-7970-review/27
I'm sure this will become even more apparent in a CrossfireX configuration. You may finally be able to install two of these side by side without having to wedge a piece of paper in between to prevent the top card from overheating.
However, despite all these positives, unfortunately the lack of CUDA support is a major problem for me at the moment, but hopefully this will become less of an issue in the future. The fan noise level is another major concern. The fan on my GTX480 is loud enough, and I don't think I could handle something that's approaching the noise level of an HD6990. We also have to wait and see if AMD has addressed some of its driver related issues, such as inconsistent performance and micro stuttering in CrossfireX.