I recenlty downloaded the X-Plane demo after being an avid FSX user for many years now. It is pretty good and the graphics are great. The flight model was excellent as well.
My major thing I've seen about it is that the landmarks and cities, etc are not true to life as it is (kinda) in FSX. Are there addons you can get that will make it so that say for instance, you fly to San Francisco, CA you are gonna see the Golden Gate Bridge in the correct location with semi accurate landmarks? This is the only thing keeping me from joining the Xplane bandwagon. I know Google.com but I figured I'd ask on here for more informed answers. Thanks and happy flying!