They are a small investment that might save you money on leaders in the long run. I have used them about 6 years now while nymphing, and I only tie up a new leader a couple times a year or if I notice one looking ratty. Otherwise, just fresh tippet added to the ring. The really small ones can get sharp if you abuse them in rocks. I use the steelhead size when euro nymphing because of that. I use them streamer fishing too, but I concur with Zipper that a micro swivel, especially in big water with big streamer, outperforms there. The ring does allow you to line up from 5X to 3X in a minute to fish a bugger, though. They work even better for transitions between drastically different tippets, and they keep a bobber in place too. I can't say I have never used them to dry fly fish, being lazy or quick in the moment, but I can say I don't head out to dry fly fish with a tippet ring on. The biggest down side is one more connection to worry about. If you are confident in your knots, they are great. But like a poorly tied on fly (whether you are rushing or in low light or blind) the knot at the ring may fail too.