After getting one of these a few years ago and utterly failing, I drunkenly bought another recently, so here's a review. The packaging/presentation/accessories have improved a lot since my last order.
The ones I bought a few years ago were a bit too big when I was flaccid, so I swallowed my pride and bought several girth sizes smaller than I had before. This fits, but barely!
My shaft is thicker than my head, even when flaccid sometimes, so trying to cram everything through and get just the glans out of the end, without getting hard, is nearly impossible. I'm uncut, and my foreskin doesn't stay retracted, which makes it even more tricky. I finally worked out an alternative method involving turning the entire thing inside out, getting the ring around the glans, then turning it back the right way round.
The second problem, I think also because I'm uncut, was getting the ring in the right place. On an uncut cock, the ring of the Stealth is sitting on the inner foreskin, which is moist, so it's really difficult (and uncomfortable!) to slide the ring up or down. It has to be in exactly the right place or the inner foreskin will bunch up and help it slide over the glans.
Even then, I've had occasional problems with the front of my glans slipping under the ring and pinching, which is not pleasant. Using the supplied "retainer band" does seem to reduce this, but it's also caused my glans to get worryingly cold at times so I'm concerned it's restricting blood flow.
It also does seem to pinch off the urethra a bit. It's not a problem when pissing, but having my glans rubbing on my underwear all day is causing me to precum a lot more, which now seems to pool in the urethra until it practically gushes out, which is both kind of hot and also inconvenient...
I'm going to try and keep using it for a few days per week at least, but I'm not sure I'd recommend buying one if you've got a foreskin. It's a lot of hassle.