I haven't seen them, but this is a small operation. It looks like a decent product, but still involves drilling the tank. I do like how it takes up very little space inside the tank.
I don't see this as being a quantum improvement over what is currently out there. Compare it to any other solution where you need to drill the tank.
Yes, there will be enough surface skimming. You actually need very little area to do that. You do need quite a bit to maintain the water flow.
I don't see any issue with running it on a SW tank. Of course you do need to keep it clean, and cleaning coraline algae from it could be a lot of work, but you'll get that with any overflow.