I can tell you the stuff is surprisingly strong. I have abused it to the extreme, and so far it is still holding.
Contrary to Masterarbor's (and just about everybody else's) very sage advice, and mostly because of my own ignorance, I used it to hold together a large live oak with a badly split stem after Katrina. I used it mostly because I had never done any cabling, I thought rope might be easier to work with, and I did not want to do anything "Invasive" in case I screwed up and had to remove and re-install it. I also did not have ready access to a big enough drill motor and bits necessary to install a steel cable system.
http://www.arboristsite.com/showthread.php?t=50324
Surprisingly enough, it still stands after 2 years. It has taken gusts to 70 mph in summer thunderstorms. I keep thinking I will get back to it with steel cables to do the job "Right", but death and sickness in the family has absorbed all my spare time and it looks like it will have to wait at least another year.
I used the "Treesave" system available from Sherrill with the slings. I pulled the branches (and thereby also the main stem) together with a tirfor before I installed the rope, or "cable", but I did not pull them together enough that the system was guitar string taught. Just enough to take a little branch weight off the split.
This is obviously abuse of the system, doing something with it it was not meant to do, but I think it commends the system that it has supported the tree as long as it has. It was very easy to install even for this "Newbie".