I think DX10 isn't even available in this demo yet, but since I haven't tried this demo on Vista yet I don't know..
However if I recall correctly Crytek at some point mentioned a DX10 demo would be out a few days later.

It smells like conspiracy talk, but on the other hand Crytek themselves said already dozens of times that they were going to implement DX10 in Crysis bút that this was not going to mean that Crysis in DX10 would be a whole different game. If you're looking for a DX10 benchmark game Crysis is not it, it's comparable to Lost Planet as far as it's DX10 implementation....

Cheers