They can be good and they can be bad.
I use them on my 14 because it is gusty in Newport, RI in the winter, all the time, it is rarely constant. But its a pain in the butt to hook up fast.
However, my experience using them on my 16 and 18 has been that it takes too long to hook up to them. It is much faster to have can't miss rings, in a race I was not willing to waste the time fooling around with the adjustments (only worth it in distance races).
Also if you leave them too slacked or they slacken up they move around and get wrapped all around your shrouds and etc.
It is really personal preference, I bought one for my 18 and tried using it and didn't like it, saves a lot of money to just try it first.
I've seen one 16 team using it but for crew only.
-Todd
P.S.
If you get it make SURE you get the aluminum clam cleat w/ roller ones. Also make sure you try several lines in it for the best fit in the cleat and one that will not wear, stretch too much or etc. The ronstan carbon ones look nice and are cheaper but after a while they sometimes just stop working (even while your on the wire). The jam cleat ones are not good either as they don't hold too well.
