It runs well, though I had trouble getting all of my hardware to work. If you are building your own Hackintosh, make sure you have the hardware supported by the OSX86 project. Other than that, I've found that it runs almost fast as a genuine Mac with the same technical specs.
A hackintosh is when you put an apple OS on a non apple computer. I have done it defore on a desktop, it worked well enough. I switched back eventually because I just didn't like it as much for a desktop. Do your research on the drivers and all that before hand though. Research makes a huge* difference and will save you a ton of headaches.