Two "M's" are good, three has to be better, right? Sorry bout that.
They are great for the right application. We use a Klein Haven's grip with a come along to pull the tree up if needed and finish the ends with Tree Grips.
Tree Cabling Equipment
I guess I should also mention that it might be a good idea to get a utility locate done if your area has under ground electric lines. We learned this one the hard way. No one hurt but knocked out the power to a five block area.