It folds down very neatly, exactly as advertised. Slim enough to slip in a shirt pocket, goes much smaller than any other smartphone mount I've seen, and in that regard would make a great replacement for whatever mount came with your selfie stick/tripod/etc (so long as that can be removed and replaced via 1/4 screw, always look for a model that can do this!)
It feels very sturdy, and the fact that it screws on means that (unless the screw strips), this won't get slack over time like a spring-loaded mount will. You can be sure your phone is not going anywhere. (Almost - more on that in a moment.)
It has an onward cold shoe mount, without which I wouldn't even consider buying a standalone phone mount. (You can attach a spirit level to get even pictures, a shotgun microphone for video, a light, etc, or some kind of onward converter to attach basically anything else that could sit on top of a phone to enhance photography/video. Why pass up on that opportunity, and close that door for yourself??) It's built into the design in a very slick way, too.
It's cheaper than the Joby GripTight Pro 2, which is my best recommendation, although that one is probably overkill for many people's needs.
What I don't love:
It's pretty heavy for its size. I suppose that comes with the territory with durable metal construction, but I actually think it makes it too heavy for the onward cold shoe to be much use on a "smartphone" tripod, selfie stick, etc. Anything with an adjustable height pole that may bend or sink under weight is going to struggle with this once it has a 150g phone in it and a light or a short stack of gizmos on top. I haven't weighed it precisely, but it's about as heavy as my phone. Perhaps I should have gone for a plastic mount - though I couldn't go past this design!
The grip pads are a bit rubbish. There's no cushioning for the phone, and they are totally flat; something curved, or something the edge of the phone would sink into just a little, would make the edge of the phone less likely to slip, and you wouldn't have to put as much pressure on the phone to get a slip-proof hold. Not super pleased about that, and will probably glue something onto the grip pads myself to address this, or at least cushion with a spot of blue tack (if that won't get stuck in my phone case).
It's also not angle-adjustable within itself (which the Joby one is), although I wouldn't try to mess with the simplicity of the design by adding that when customers can just mount it to a mini ball head (<$5 including delivery) if they want it to move around. (I personally wouldn't buy another mount over this one because of that feature, especially if there were other trade-offs.)
In short, this is a fantastic design, but it still needs a bit of work to be wholeheartedly recommended. A subsequent generation of this with a little reworking could blow every other phone mount on Amazon out of the water.