A friend had a tree that developed a perilous lean towards his power line after some recent wind. So we went over there after work today to see what we could do about it. Because it was leaning towards the power line but was still quite a ways from it, we could safely drop limbs starting at the top and working our way down (if we'd dropped the whole tree I'm about 50% sure it would have taken the power line down with it - it certainly would have hit it pretty hard anyway). To take off chunks of the limbs he had a rope saw - which worked waaaay better than I'd imagined they would. They are really best done as a two person operation though, with only one person it binds pretty bad because the angle is to shallow (with two people you can stand off to the sides as well )
I think the one he had was something like this: http://www.amazon.com/High-Limb-CS-4.../dp/B0000AX849 - although not 100% positive on the exact model.
So from someone who just went from a skeptic to a believer; if you need to do some limbing and aren't to bad at flipping a rope over a limb these work pretty darn good.
I also got a couple little chunks of wood for a project out of the deal We'll see if it works out.