Games like DiRT2 that use DirectX 11 are due out before the end of the year, so it'll be really interesting to see how well they perform. DirectX 11 is included in Windows Seven and will also be available for Windows Vista. Like DX10, DX11 is not available for Windows XP. Another thing that is noteworthy that the DX11 cards themselves also do not support Windows XP.
From what I know, the Nvidia DirectX 11 hardware is due out in late 2009 or early 2010, so there will be a greater choice of hardware in that time frame. The prices of the cards should go down with the competition between AMD/ATI and Nvidia in that same time frame.
Feel free to add any additional DX11 information to this thread. I'll update it periodically with anything else I find on the subject.
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