I wouldn't mind trying that thing, too. But I suspect I know what will happen. It will work great as long as there is a big mass of unsplit round creating serious inertia opposite the slab you're whacking off one edge, but once you get down to the core of a big red oak or white oak round, all bets are off. The grain will be too twisted on the white oak and will either bounce off, stick in, or tip the remaining part of the round over when the rotation occurs. The red oak center will be too dense, and /or twisted, and also lack the mass for inertia required to offset the twist action and the round will tip over. I suspect this is why the pictures show the use of a tire to keep the round together enough to maintain enough offsetting mass after most of the round has been fractured. I don't think I'd use a tire myself, though. Seems like too much trouble to me.
But, like Corey, I'd be willing to try it. Since all I have to split is maple right now, it would probably do a lot better than on oak, so maybe that wouldn't be much of a test for my typical wood of choice around here (oak), but might help someone who splits a lot of maple.
On the other hand, is there anyone here who would actually cough up $250+? bucks for a splitting tool? My 12 lb Collins maul and 8 lb Ludell only cost about $60 all together! I'm not sure that thing would even sell in my yuppy neighborhood. Not many of my neighbors even chop wood.
[added] I use a technique similar to this, as I know many others to, when I'm starting a new round that is over 16 inches in diameter, or so. By hitting the edge at an angle away from the round, a big slab of wood usually pops right off, but this ceases to work once the round is whittled down. At that point, it would just tip over in the direction I was biasing the swing.