I have seen and dived one. As a gas extender it works quite well, although it does so in quite possibly the most complex way possible. I had significant problems with getting it started and through the checklist (think multiple tries, even the instructor had issues), but once done it was fine. However it's still an SCR, so it still vents, and you are still limited by NDL. Bailout was nice and easy, I think that's probably the highlight of the unit, Hollis did a good job on that. My experience was enough that I decided to pass on buying one, and either work out to dive a large single, a stage bottle, or go full CCR.
Again, for a travel rebreather, you're still looking at the logistics of it all. If there's no sorb available, you've gotta bring it or ship it. Sure you can bring a couple of EAC cans, but either way, it's still a problem of supply. You've still gotta bring your tank or try and work it out beforehand to see if they've got an acceptable size. The number of dive centers that have a decent stock of them is rather small, so don't count on getting much support parts/maintenance wise in most of the travel diving world.
I think the Hollis rebreathers niche is the guy that likes diving a rebreather, does the same dive regularly so he can match the mix to his standard dives, either blends his own fills or has easy access to getting his tank filled with whatever he wants, and has ready access to sorb. Basically, a local diver who maximizes the potential of the unit. As a recreational rebreather, it works as designed, removes the gas limitation on NDL dives, and works great for someone willing to thumb a dive before he gets in the water when it gets pissy. None of those are really conducive to being a travel rebreather.