It's normally smoother for the eye, you'll see it easilly by zoom all the way out, and look how awfull the fine sword of the hero looks like, it's like stairs. With AA, it should be smoother.
The price to pay for activating FSAA, normally some performance.
But the game is then unable to do screenshots or to get the mini screen for the savegame. And when loading you'll see the intro screen instead of the game screen.
