We used one in our efficiency vid, and they are nice but there are a few tricks to using them:
1) Be careful tightening the "backs" on, seems like whoever did their machining didn't debur some of them all that well before sending them to anno. I got a bunch of paper cut-like cuts on my hand from the first time I tried to tighten the thread adapter on by hand.
2) The holes in the adapter are there to stick an allen wrench through for leverage to tighten the barrel in. Snug it up really well because it's reverse threaded and if you start to tighten it into the gun with the threads even remotely loose, you'll undo it.
3) Transfer the o-ring from another barrel (the one we used didn't have one) to keep it from loosening up if you're using SP threads.
That's all I've got. They're a great solution for having multiple thread types in your stable.