I think I'm using FIXED in my game, its similar to Unlimited in that theres almost no input lag - everything is more responsive. Theres a bit of tearing, but if the player wants less they can bump up the FPS of the game I figure in an option (theres a set FPS action thing for fixed).
Since theres no option to turn off v-sync during runtime, I think the only option for action/fast paced games based games like platformers/etc is to use Fixed framerate so theres less input lag.
I think the only time you should use v-sync is if its a turn based, or a game where precise quick movements isn't a key part of it.