I'm really torn on them. I love the concept, especially their purported reduction in heat, but I don't think they are quite there yet.
Their original hexagonal tube design was atrocious, weighing way too much and being 150+ dB at the muzzle. The new Helix QD design has brought weight down to be similar to comparable sized suppressors, but unfortunately their dB measurements seem rather 'meh' to me. A conventional suppressor with an adjustable gas block or BCG can easily get similar or better numbers, both at ear and at the muzzle.
I'm also rather turned off by their gimmicky sales pitch style videos. "Oh, look! This conventional suppressor got carbon on my white t-shirt! This is a real problem that must be fixed!"
They do live up to their claim of reduced back pressure and minimal increase in bolt velocity, though. If a person wanted a suppressor they can easily run without the hassle of tuning an AGB, they are a good option.
Personally, I like the proven durability of a full Stellite baffle stack made by a reputable manufacturer, with a good warranty and a history of exceptional customer service. I'm not saying OSS isn't reputable or won't back their warranty, but they are certainly no Mike Pappas. They are still the new kids on the block in my eyes and have already changed ownership once, though they seem to be stable at this point. I just happen to be very cautious when it comes to the possibility of another Huntington Arms fiasco, especially for a suppressor as complicated as the OSS.
Just my personal opinion though, and worth exactly what you paid for it.