Evil-- Yeah, these have my interest as well. Haven't heard much about their use, and I'ma skeered to be the guinea pig. There's a guy on STN who just put one of these on and I'm waiting for his report...
I read a post on another board about the screw type master link.
Sounds like you need to use the same care as you do when installing the rivit links.
I think in the post, the person installing the link thought he had it on tight enough, but he lost the link while riding.
I asume it is easier then dealing with the rivit type link, but seems that getting it, not to tight and not to loose, are just as important as with the rivit links.
Sounds like an easy solution for those who don't have the tools to rivit the chain, but care must still be taken, so for some it may still be safer to have a reputible shop install rivit links on those new chains.
Perhaps use the screw type on the new chain after you've done all the work of changing sprockets/chain, then if still unsure ride down to the shop and have the rivit link installed for a couple bucks.
Guess we'll just have wait and see how the new links hold up as more people start using them.