I do not have one now but thinking of putting one on can anyone tell me if there are any advantages to having one?

less serving/string wear, and they don't ("pinch") the nock, i've been shooting one for the last 3 yrs. with no problems

pretty much what m.t.hands said. I also heard that you will gain couple ft/s. I started out w/o string loop, but I am very satisfied with the string loop. No more string wear. I haven't confirm the ft/s gain, though.

3 years now, no problems

I have one and love it. Saves on the string. I put one on my AR because of the peep sight I have. The peep has no rubber tube and was having problems with it not ligning up every time I drew back. The loop makes it perfect every time and still do not have to worrie about the rubber tube breaking.

As for speed I have been told it will reduce it a little because you are shortening your draw a little bit. But then again you are loosing the weight of the nocks. Who knows? Who cares? Its not enough to notice by the average hunter.

I like it, I use it.