Spent about 3 hours tweaking graphics settings to get this running on my 13" MBP (Early 2011).
Got it running at a smooth 30fps, scenery is at a bare minimum. GA at 25%, airline at 55%, no cars or boats etc. No auto-gen, but scenery is at medium. Aircraft are "ultra-high", with all animations and shadows etc. Antialiasing is turned on too, just smooths it out, running at native 1280x800; not too bad for integrated graphics but pale in comparison to some of the pictures in here!
Luckily the textures/scenery in FSX makes things look great anyway, and I've never been big on all the scenery. Maybe in the not-too-distant future I'll be able to afford to put together an absolute beast of an FSX rig like Soya's, but for now I'm very pleased with the state of play on my MBP.