DirectX11 facts unveiled from joystiq.com

[Oreo]

Maybe it's just much harder to acheive the same effects in DX9 as achieving them in DX10. which means Dx10 is more efficient, and games get released earlier ??

Maybe not, but it would make sense.

 

[Apokalipse]

Maybe it's just much harder to acheive the same effects in DX9 as achieving them in DX10. which means Dx10 is more efficient, and games get released earlier ??

It's more effort, but I wouldn't say it's "much harder".
Even if it was, that doesn't mean DirectX 10 is more efficient.