FSX SP1 is live!
You can download the English, French, Italian, German, Spanish or Polish versions from our website. The Japanese version is a day behind and should be up soon. I think you will be pleasantly surprised with the performance improvements in SP1.
A lot of work went into making this update really worthwhile. We found some pretty major bugs. For example, the old FS9 aircraft that we hadn't updated were using an insane amount of draw calls. The Dash-8 was 225 draw calls and is now 14. The Cherokee was 245 and is now 13. The MD83 was 375 and is now 12. So between those three aircraft, we were at about the recommended number of draw calls for a scene. Needless to say, turning on AI aircraft should be a lot more performant. We also batched the autogen a lot better and fixed a whole bunch of other performance related bugs (as well as started to offload some tasks like terrain rendering to the other cores of a multi-proc machine).
Unfortunately, the fresnel ramp is still a bit messed up. It sort of works, but doesn't really sample as it's supposed to. I wouldn't recommend using it for anything except special effects (which is what it's really designed to be used for anyway). We overused it in FSX and will be scaling back significantly on its use moving forward. It's really ideal for things like two-toned paint schemes and controlling reflections. Because it is a multiply, it doesn't make much sense on specular (unless it is really colored) because all it does is dim the specular down. At any rate, we will be fixing that bug with the DX10 update.
Have fun with SP1! I think you'll like it.