I`v go the demo, and after few h of flying I pre ordered my copy of Xplane-10. It looks, works and feels much much better than Xp9.
-greatly improved flight dynamics, the planes are no longer rc toys
-few new planes with full 3d interiors and many working buttons.
-3d clouds and new weather. No more silly 2d bitmaps in the sky!
-better looking scenery. Ground textures are not super fantastic, but roads, buildings and lights are very nice.
-new ATC with nice voice acting.
-self shadows on the planes (finally!), and engines that generates heat blurr effect.
Those are things I`v noticed so far, but I`m sure new Xp has a lots more cool stuff.
here are some pics with KC: