Gotta say don't get along with any of these. Had the very first incarnation of those things already (I think it was the Rockinger Blackbox beginning of the 90s or so) and while they've certainly gotten much better, they all have one thing in common: There's no smooth vibrato around the zero position. And quite obviously, you can't do anything about it, it's just the nature of the idea.
The only thing that ever did a great job (and it was a pretty much perfect job) has been the Steinberger TransTrem. Grab the bar = free floating vibrato smooth as butter, put bar back down = fixed bridge. Really, it doesn't get any better. Just that the guitars IMO sucked big time, which is why I sold mine (in retrospective, I shouldn't have done so, though).
It's pretty weird that nobody ever came up with another decent version of a vibrato lock, it'd be all doable, even as an aftermarket thing and for pretty much all vibrato types.