The HD 6790 is designed to thread the needle between the HD 6850 and the HD 5770 (also known as the HD 6770 to our OEMs). Based on both the performance and price points, it does this perfectly. In my review of the HD 5770, I said it was, "the tipping point in the HD 5000 series". It was the card where gaming prowess started to show up, albeit primarily on single widescreens.
The HD 6790 fills the same function within the HD 6000 series. Most games we tested hit 30fps at max settings on 1920x1080, and they all basically hit 30fps at 1600x900. A handful of games will hit 60fps at either 1920x1080 or 1600x900. With a few tweaks to settings, most any game can be run at 60fps on a single widescreen.
A handful of titles will hit 30fps in Eyefinity at either 3x1920x1080 or 3x1600x900. With some tweaks, most games can hit 30fps in Eyefinity. The only hold-outs would be newer, more intensive games such as AvP and STALKER.
The HD 6790 is a very capable of card that will fit many gamers needs. I didn't have a second card to test CrossFire, but I would suspect CFX performance to fall between that of the Radeon HD 5770 and Radeon HD 6850 CrossFire numbers.
The HD 5770 launched 18 months ago at a price point of $175. The HD 6790 comes in with better performance and a lower price point of $150. This pricing is a "hard price", with no rebates or discounts offered. While this is obviously a better value than the Radeon HD 5770 was, the question is: Is it the best value right now? Probably not.
If you're diligent with rebates, you can currently find a Radeon HD 6850 for $155 or $160 with rebates. This increase of $5 or $10 will bring you a considerable increase in performance. If you're on a tight budget, and/or are bad with rebates then the HD 6790 is a great value and a great choice in the AMD product stack.
Finally, while the reference design utilizes two 6-pin power connectors, PowerColor is offering a custom design with just one 6-pin connector. If your power supply won't support two 6-pin lines, then this would be a great option to improve performance in your machine.