The cutter is a great pitch, some advice though if you throw it in high school games make sure your catcher says something to the umpire about throwing the cutter. When I pitched in the summer I had my catcher just say that I throw a fasbtall with late movement and to wait a second before calling the pitch. It worked pretty good and didn't have a lot of problems.
I've seen Mo freeze up pro umpires many times. I like the pitch a lot it really will confuse a batter. The pitch really is a slider that is faster, and doesn't break as much, except its easier to locate and with practice can be thrown for a strike just like a regular fastball. Perfect exmaple is Mariano Rivera.
One time in the summer after my first inning I noticed what doesn't usually happen in the summer, all the kids were focused on the game and talking. Then after each cutter I threw I noticed the blank stare the batters would give me. Next inning two of the coaches were standing near the 3rd base line watching me pitch, arms folded with that same blank stare. Of course I wans't pitching against good competition but you get the point. It is a pitch that will decieve hitters. Especially good ones. The ones who are trained to let the balls go and swing at the strikes.
Why do you think pro hitters are pro hitters? They're good thats why. They are trained and after years of baseball experience, to let the balls go. So when Mariano throws his cutter inside to a RHB he says ok ball, even though the batters knows it will end up as a strike his instincts tell him not to swing. So he either doesn't swing or takes a bad swing at it.