2 points.
1) DX10 ain't worth it cause MOST add-ons don't work with DX10.
Some, not most!
2) There aint much difference in DX10 compared to DX9.
A massive difference on the right machine, FPS is a lot higher-everything is smoother
DX9 is far better in FSX then DX10.
It depends on the machine and the software/system, just because yours is crap does not necessarily follow that everyone elses is the same! DX10 on the right machine/system with adequate drivers will be faster and smoother but still possibly suffer shimmering. The drivers will inprove this as time goes on. Maybe you need to look around a bit more and experience different setups before you make these wild and obviously ludicrous statements!
It is ofcourse a different ball game when you play stuff like COH and WIC. Those games were made for DX10 ;)
So was FSX with SP2 and a DX10 compatible card, it was made for the DX10 preview and that is what you get. Comparing this to a game that runs full DX10 is like comparing chalk to cheese, we all know its going to be so different and really does not need to be said!