Otherwise known as the 'death hitch'. NOT RECCOMENDED to any but the most experienced, even then it can still bite you hard.
While it may work great for emergency belaying while mountain climbing, it really has no place in tree climbing, in the tree, used fpor rappelling, it is completely dependent on the climber holding the carabiner, and the rope properley, sounds easy eh, but one wrong move the whole thing twists and youve got free running rope thru a beener, I speak from personal experience having taken a twenty foot ride to the ground landing on my sore ass.
That was the last time I screwed around with the ol death hitch as I now refer to it.
NOT even close to being worthwhile, tie proper knots(is it worth saving a minute to put yourself in harms way???), or if you just want too zoom down the rope, your just setting pull ropes and want to have some fun rappeling down single lines, use a figure eight. While eights are still rather dangerous and must be used with care and proper technique, they do not have the ability to untwist leaving you with rope running through a hole(the beener, its hard to explain this stuff in words, but if you have the gear on and you set a munter in front of you you should be able to see what I refer to).
IMHO the munter is just an accident waiting to happen, leave it to the rock climbers and rope rescue experts.