I own one, and you do have to be VERY careful in how you use it. Mine is about 100 HP +/-, and has a drum about 15 inches wide and 12 inches in diameter. It will chew up logs nicely. Not well suited to small brush...
Experience has shown that if something goes wrong, killing the motor with the drum engaged will shut it down in just a couple seconds. That said, I don't want to test that theory in an emergency situation. I found out "the hard way" with mine when it threw a knife. Made a heck of a mess of the safety shrowding...
-Tom