Quote: "MS shot themself in the fooot not letting DX10 be used on XP."
I'm sure if it didn't rely on WDDM and DXGI, it would be released for Windows XP. What I think is realistically shooting them in the foot is having DirectX10 force the use of the Geometry Shader (SM4 Only) that only DirectX10 cards can use. Yet the design of the DirectX10 model is focused around those card that don't fall-back on Fixed-Function pipelines (as it's been removed).
I mean one of the key aspects removed is Transform & Lighting, for the Geometry Shader; but it's entirely possible to have a pipeline that is not fixed function with just the Vertex Shaders.
So realistically if they took out the Geometry Shader requirement, then cards down to Shader 2.0 would be able to happily run on it..
GeForce FX or later, Radeon 9K-Series or later
but they could really push for Shader 3.0 only cards so that the entire back-end could still remain shader driven on Scalar Shader Unit cards.
GeForce 7, 8-Series and Radeon X1K, HD-Series. Given these are the most common; personally I would've made the decision to keep cards that are deemed "Vista Essential".. as if that card is the minimum to run Vista with Aero; then having them be able to use Dx10 would not only mean there is a base card that could be used, but also Aero itself could be accelerated from the Dx10 performance enhancement.
Vista and DirectX10 on the whole have not felt quite as well thought through as the original design they proposed 5years back. So many things make little sense, and rather than keeping aspects of compatibility that has made Windows so popular over the years, they've replaced that with 2 types of user.
Those with normal computer users, and DirectX10-Generation users.
After spending $250 on a new OS; why the hell would any user want to then spend another $250 just to be able to use Dx10?
More over their Live service which was promised for release is still a few months off for public use. This is a serious ball-drop imo, especially when you consider it's first titles Halo2 and Shadowrun have been getting slammed for poor games across the service.
Halo2 has trouble connecting, and you can't play with Xbox/Xbox360 users; Shadowrun while a cool prototype game, in all other respects need MUCH more work .. and the Live functionality feels like a last minute addition. Given the team sizes working on both with these being the flagship titles for the Games for Windows Live service it doesn't really bode well for them pushing it for developers to use it.
What's more is Live is another Vista-only product. Without it working seemlessly (or rather close to) as it does on the Xbox/Xbox 360 then this is just going to put pressure on people to remain with XP for a bit longer.
Ironically Uno, the free title you get with Games for Windows Live; and will be shipped with Vista's second release, actually plays exactly like the Xbox 360 version. Works identically and with seemless Live integration.
Kinda amusing when you realise that a small independant team of about 10 people worked on it. It even has Live Video and Audio, something the other games die at trying to use.