I'd say read something from game developers before you say anything about "Vista fanboi"s, AshenSugar.
http://www.extremetech.com/article2/0,1697,1989806,00.asp
"we also have a few ideas about how to use the geometry shader to do effects that are impossible on a DirectX 9 card"
" the person with the old card is going to see less, have a lower resolution and pretty bad lighting. On the older cards, we will try to draw as much as we can, but we might need to cut some corners, draw some low LOD versions of players and monsters, and possibly pull in the far clip plane. We are going to make every effort to make sure that there isn't a gameplay advantage to having superior hardware, but the game will look radically different between our very low min spec and the DirectX10 version"
"A DirectX10 graphics card is a big technological step from the previous generation of cards. Not only are they going to be a big jump in polygon counts and pixel fill rate, they give developers many, many more tricks that they can do. I think that most games are going to have a big visual difference between what a player will see on a DirectX 9 card and what they will see on a DirectX 10 card."
"xtremeTech: DX10 adds quite a few significant new features and changes to the API (and hardware requirements)—stuff that may potentially change the way games are made. Which new feature matters most to you?
Yerli: The geometry shader, together with texture arrays, can greatly simplify some render-to-texture operations. This can speed up things like shadow computations, reflections and refractions. "
"Edlund: Integrating DirectX 10 into our application will allow a much richer and more detailed world to be rendered at equivalent frame rates. Over the next releases, we will be continuing to increase the level of realism, detail in the world and world objects, dynamic lighting and subtleties, weather effects, and extending the capabilities of user interaction, exploration, and camera control in our world-spanning rendering environment."
"DirectX 10 will allow developers to take advantage of more of the DirectX 9 functionality, in addition to the new DirectX 10 features, to create more realistic scenes, not just showcased objects, then ever before possible. Supporting this is a more stable and coherent driver architecture that will end the days of driver crashes interrupting your game experience. By freeing the CPU up to do more game-related processing, you will see a quantum leap in the depth of AI, physics, character interaction and realism that becomes inherent in the next generation of games. "
"Godager: Because of the different architecture of the DX10 system, I think the biggest difference will be in the richness of the content. There will be more objects, more characters, more particles, longer view distance, more grass and foliage."
"any things are easier to work with on DX10. We can move several things from the CPU onto the GPU, like pre-skinned characters; geometry shaders will save bandwidth, texture arrays will save draw calls, and it's a generally more-efficient API. All this adds to a more effective rendering engine, giving the programmers more freedom to do other things they want. We are quite excited about being among the forerunners in DX10 game development and hope to be able to give players a richer, fuller experience when they invest in this hardware."
"DX10 is more than just a gradual extension of the DX platform."