I posted in the other thread, but I guess I'll post an edited version here too.
I've been using one of the new tailcaps for a few months now, and I'd I haven't found any down side to it. I've never been a fan of needing to use tools to open a piece of gear to change batteries, and in the case of these pieces of functional titanium art I was always worried about scratching the finish. Also I don't use a lanyard, I use a belt pouch, so the bead wasn't really an option.
When I got the new tailcap, my first and only fear was that contact through a thin sheath (or pocket bumping) would cause it to fall off. This has never happened, even though I have tried to make it happen through testing in exaggerated versions of real world scenarios (basically frequent fidgeting and fiddling).
I like the idea of a semi-waterproof tailcap, but for EDC in normal circumstances, this quick-release is excellent, and I've been wanting a second one for another light. (I've tried it on both a Tri-V1 and 2, and left it on the 2 since that's what I carry.)