You need to be able to run a HIGH refresh rate on your monitor to get decent image quality. 120Hz is the absolute bare minimum with 150Hz+ being preferable. This is because the LCD screens in the glasses act like shutters to display the slightly offset images your screen will now be presenting in alternate frames. So if you're used to using 75Hz for your game, you now need 150Hz since there're twice as many frames being displayed.
On the whole, it was kinda neat back when I was using mine. Some games worked better than others and it took your eyes/brain a little while to adjust to the effect. But once you relax and get used to it, you'll suddenly find yourself moving your head to the side in an effort to peek around a corner. Which obviously doesn't work all that well.
