Just so that you get the full range of replies here is mine. I got one of the kits and have tried it a dozen tomes or so. In my opinion you have to fiddle with them over and over to get them attached correctly, they do no do a very good job of floating a weighted nymph, and they soon absorb water and refuse to float without more fiddling. They seem like a great idea but in my hands fail miserably.
To each their own,
David