Someone posted about these things a LONG while back on Hiking HQ - I think it might've been Turk, actually...
Anyway, I checked out the website
and for the price, I couldn't resist. They looked like a good idea, and I'm a sucker for gadgets.
I put two on the ridge tie-outs (the ones that go to the trees) on my tarp, and I got to try them out this weekend in Uwharrie with Slowhike. They work incredibly well! They make adjustment, centering, and tightening SUPER easy and quick. The best part is, they're tiny - about the size of the end of my thumb - and very VERY light. I haven't weighed them, but they couldn't be more than a couple of grams apiece. IMO, definitely worth it!
Here's a pic, courtesy of Slowhike: