In Accel/SP2 major changes to shaders have occurred. Phil discusses some of this in his blog. Older video adapters may have problems in both DX9 and DX10 however most modern adapters with better shader support should be fine, but, will most likely have a few quarks to overcome which are directly related to the hardware and drivers and it is not all about FSX.
This is from a Aces developer
http://www.sebbylive.com/Articles/AboutMe.aspx
http://www.sebbylive.com/?tag=/performance
[quote]
My point of view is similar. The two main components in my opinion for poor performing DX10 titles are the abuse of DX10 features and the lack of maturity of DX10 drivers...
The second aspect, well, we don