Have looked at this implement more than once; I use a Bobcat soil conditioner with my A300, and have a Bradco land plane hooked to a Tilt-tach for rough grading. About 70%-80% of my topsoil/lot prep is on ground that is thick with embedded river cobble, some with sand/clay binder and some with pure clay - that stuff tends to be tighter than bark on a sapling. Basically what a guy tries to do is get the worst of the rock pushed aside, and then grade with whatever half-decent material happens to be left over. Often that's little better than smaller rocks as topsoil is spotty here and the screened stuff is high $$. Then the next problem is harley raking the trucked-in soil, as it too is often high in clay. Depending on moisture content, finishing consists of one pass with the grading bucket, one with the rake, and occasionally I have to make do with a single rake pass to grade and level. Any more and the soil is compacted more than you want for starting sod or seeds. It is for this dressing pass I'd been looking at the SR3 option.
The other thing I noticed in the vid is the implement's need to be working the grading pass backwards. On town/subdivision lot jobs, 90+% of the time I'm working behind the sprinkler guys, so I've already got all the heads, junction and electrical boxes installed in the yard. In some areas, well flow rates are not that high so they install quite a few smaller zones instead of bigger ones. With a small forest of those things, especially on small lots, working backwards is certainly possible but slow. Working my rake forward and using the hydraulic angle function is fairly effective windrowing and pushing soil into place while avoiding all those obstacles.
I'll be interested in hearing further how the SR3 is working out for you.