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1.Multi core processor support in the engine: Oblivion wasn't multithreaded and neither was Fallout 3 so vote for this if you want multi thread support.
2.Implementation of one of the latest Direct X APIs: This could be of course DirectX 10.1 or 11. There are some nice feaures in DX 10.1 like ambient occlusion, SSAO and Gather4. Implementation of http://www.legitreviews.com/images/reviews/584/DirectX%2010_1%20White%20Paper%20v0.4.pdf definitely would be a good step over DX9 TES IV. But it's http://en.wikipedia.org/wiki/Direct_x_11#DirectX_11 that brings us Shader version 5 and Tesellation.
3.Implementation of proprietary technologies like Nvidia's PhysX: Maybe some of us find such proprietary solutions cool and want to see in next game.
4.Trouble free support for scalable graphic solutions like Crossfire and SLI: Personally i didn't see any improvements IN OBLIVION after adding second HD 4850 to my system. I checked graphics cards usage manually. There i saw Oblivion utilizing second graphics adapter but both cards loaded maximum %60 in contrast to single card is loaded %100 all the time. So there was something hindering the extra power and it was not my hardware. In Fallout 3 there was a lame issue with HDR lightning and multiple graphics cards.This was never fixed. If you enable HDR lighting with SLI or Crossfire then sky starts to flicker as you move around. So annoying indeed. You can google it and see how people with multiple cards had to turn off HDR to play this game. If you want Bethesda to solve such problems, your vote belongs to here.
5.Official support for OpenAL based Creative EAX Advanced HD to make 3D sound work under Windows Vista and 7 using Creative ALchemy software: After Microsoft removed hardware layer from Windows sound we could no longer use sound effects like EAX or any kind of 3D positional audio. Because such technologies are based on Direct Sound and direct sound uses hardware layer to communicate sound cards. Since Microsoft removed it from Windows, all expensive Creative sound cards became as useless as onboard sound chips. Then Creative announced that there's actually a way to bring all these features back using an open source sound library called OpenAL. They developed Creative ALchemy and released on their website for free. This software basically simulates Direct Sound commands using OpenAL so you have your sound effects back. But then again there were only few games supporting OpenAL and unfortunately it was impossible to bring back these features for non-OpenAL games. These games had to use 2D Windows software sound. If you don't want TES V to be one of them, then vote for this.
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P.S. Please remember all we're trying to achieve here is to increase quality of the next TES game by collaborating so please don't start any flame wars based on ATI, Nvidia fanboyism. Thanks.