We had a chance to briefly talk to one of the key chaps behind Microsoft's Flight Simulator X, a Mr Phil Taylor and he confirmed that the Flight Simulator SP1 patch is going to significantly speed up the game.
A lot of users responded and said that they are getting much higher frame rates than before. The most important part is that you can utilize all four cores in your quad systems and the game runs faster on quad cores than on dual cores.
The DirectX 10 patch is still in the works and I can imagine that the chaps are testing it on the R600 hardware before they finally ship it out. That was the original plan.
You can get some more details here.