Well, I just exhausted the demo time limit, and my interest is piqued.
On my hopelessly-outclassed rig I got my usual 20-26 fps at the very low default settings (with lots of framerate-jumping),and at near-max settings it looked beautiful (water especially) but yielded about 2 fps. :D
The easy flexibility of the new view modes is very nice, but I'm not so sure about the visually-indicated g-effects... I doubt that changing the prop setting by 100rpm either way in the Beaver would knock your head around like that in RL. And in general, the head movement they're trying to simulate , whether one is accelerating/decelerating or turning, distracts more than it enhances realism. In RL, these sensations are felt rather than seen... they may have been better off leaving that alone; it's a very, very subtle thing that's nearly impossible to model without actual motion. But I'm sure that's tweakable, or it could be disabled.
VC cockpits look fantastic, but so do some of the default FS9 VCs.
I'm planning to start my next build this month; still building for FS9, but I think it might run FSX pretty well, even without Vista.