I just got one last month and am absolutely in love with it. I use it with my VapeXhale Cloud and needed to buy an 18mm Fem-Fem adapter in order to make it work, but the results have been spectacular. Easy no regret buy, and hey kids, it's absolutely beautiful to look at as well. A true art piece by a blower at the top of his game.
If there are any criticisms, you have to be a bit careful in that when you're done with a session, or when passing it around, the occasional air bubble might splash back a tiny bit of water up the stemless tube when tilted slightly. For my purposes, the extra height of the adapter solves that problem anyway, but I definitely remove the vape before moving the Bubbler. i suppose that aspect has created the most discussion/concern when using a nail. Not a relevant problem for me and really, the true answer here is JUST DON'T MOVE IT while in use. Also, some people just fill it way way too high and that's improper use IMHO.
Also, I've only used it for vaped flowers so I can't speak to it's dab potential but again, it is unmatched to anything else I've ever tried, including the Cloud's native HydraTubes. You'll be amazed at it's incredible incredible silky smooth diffusion. It will stack to the top of the can effortlessly if it's "unplugged" but still does a great drag-free job when in real use. I fill it to about the 3/4 mark on the top perc, and while it would appear that only the top perc is bubbling while in use, the bottom matrix perc is used to reduce drag so people will sometimes confuse the real purpose of the bottom perc, but I think that is probably the true benefit/advantage of the stereo.
I'm just about ready to add a demo video to the Cloud thread so keep an eye on it over the next week or so.
My understanding without having tested it personally is that the dewaar is slightly more harsh given it's travel vs. the stereo. As such, I had heard that the Dewaar might have more taste with it's slightly less diffusion and smaller size, but I'm telling you first hand, the stereo has incredible taste, and I can't imagine that I'm leaving anything behind when using it.
Highly highly recommended.
Giant Robot
Edit: just added a Cloud vid on page 110 or so of their thread, and spent a bit of extra time with the bub so you could see it in action.