D.B.
My son didn't really like them - used it once as a newborn for about 20 minutes and that was it. The down side, from those who have used them, is that they fall out and either get lost or dirty (unless you use one of those things that attaches to it), and they can't put it in their mouths themselves. So they get super frustrated, and the parents spend all their time reinserting it. But the good thing is that you can eventually take it away. (Google "Binky Fairy" for that technique for an older child.)
My son loved his thumb. The good part is, he could never lose it. The bad part was, we couldn't take it away. He needed braces but then again, many kids do for other reasons.
Personally, I think you do what works for you. Kids calm themselves down in a variety of ways. There is value to calm, to good sleep, and to just going with the flow with babies.