and

"My video card is the ATI X1600 with 256mb vram on a refurb MBP 17". I am running Microsoft Flight Simulator X at native resolution however I can only get 7-10 fps with the settings on high (Both scenery and aircraft...I kept the traffic setting on low). I lowered the "Autogen" setting and now I get 12-16 fps. It is playable now but seems to lag over the big cities. When I try to lower some of the settings from Scenery and Aircraft..the fps only goes up by 2-4. So not a majot change. Yet in the demo I would average over 20fps with the same high settings. I even went to try the default airport (St. Maarten) that was used in the demo and it achieved less fps than the demo version. Strange. From what I have been reading in online forums, Flight Simulator X only uses one core of the CPU (now why would Microsoft do that when they know multiple core processors are the future and present). Seeing FSX as both a CPU and GPU intensive game, MS should have designed it to use multiple cores which could have helped with performance."

(Moderator edit (BG) - Hyperlinked URL)

It's a universal binary, graphical requirements aren't too high. The demo is highly restricted, only 5 minutes of controlled flight and only scenery for a small patch of California.

I don;t believe you can legitimately download the full version, only the Demo.  You have to order the full version on CD.

May be their method in managing illegal distribution, and may require the CD in drive to play (similar to many other major games)