I had a chance to try one yesterday at the quarry with guru Steve Lewis. Since I have virtually no sidemount experience, it would be hard for me to give a comparative opinion. But here are my newbie impressions.
It fit me very well, a little better than the SMS75 that I also tried on. I have limited shoulder mobility and a long torso, so the longer HOG put the butt rings in a more accessible spot for me. However I think the design would be a little better if it were 2 pieces instead of one. Although the placement is adjustable, the overall length is fixed. I don't know how else to describe it. With my long upper body it worked fine.
Quality seemed reasonable, but not bulletproof. And there were some issues. This could happen to any rig, but my first pull on the dump valve immediate broke or untied the knot so that the entire dump cord pulled out. As I was already in the water with tanks on, it was not convenient to take the entire thing off and fix it. I tried to stuff it in Steve's pocket, but it eventually was lost. Not a great start. Trying to fine tune bouyancy by dumping with the inflator was a bit of a struggle and position related, but that was probably more due to my inexperience with SM. Couple this with one of my HOG second stages breathing very wet and it became a bit of a frustrating HOG day even though it was probably my fault.
Overall it was a good experience and the rig seems to be a good value.