Final ThoughtsRegardless of the lack of DX11, The Witcher 2: Assassins of Kings is a visually stunning game and it's right up there with Crysis 2 as the best looking DX9 titles around.
While patch v1.1 delivered a much-needed performance boost, The Witcher 2 is still capable of bringing today's finest hardware to its knees. UberSampling cripples every single-card solution available, including the dual-GPU GeForce GTX 590 and Radeon HD 6990. You'll need a couple Nvidia graphics cards to experience the feature as it doesn't seem to work properly when using Crossfire (for now).
Technically speaking, neither AMD nor Nvidia currently offer official support for multi-GPU technology in The Witcher 2. The AMD Catalyst 11.5b hotfix driver does enable Crossfire performance, but hotfixes aren't backed by AMD and there are still visual quality issues surrounding lighting. Meanwhile, SLI requires you to manually create a profile using the value "0x02C04205".
Although there are a few differences between Ultra Spec and High Spec presets, such as the texture memory size, shadow quality, number of shadowed lights and LOD distance, we didn't record a speed difference once we turned UberSampling off. We recommend that gamers skip the High Spec preset and use Ultra instead, while making sure to disable UberSampling.
In doing so, affordable graphics cards such as the Radeon HD 6770 can provide reasonably playable performance (30fps) at 1680x1050. If you want to play maxed out (sans UberSampling) at 1920x1200, we'd recommend a mid-range product such as the GTX 560 Ti or HD 6870 for ~40fps, but you'll have to enlist the power of the GTX 580 or better if you demand 60fps+.
You should also be aware that this is not strictly a GPU-dependent game, as it requires quite a bit of CPU power. We recorded a 58% performance gain when increasing the Core i7-920's clock frequency from 2.0GHz to 3.8GHz, and Intel's new Sandy Bridge chips outperformed every other platform tested. Additionally, dual-core chips were about 25% slower than quad-cores.
Overall, we've found that The Witcher 2 scales quite well, covering a broad range of today's hardware. On one end of the spectrum, you can scrape by with an affordable graphics card such as the $80 Radeon HD 6570 by playing with the Low Spec quality preset. On the other end, you can quite literally incapacitate today's fastest dual-GPU cards, the GTX 590 and HD 6990.