It doesn't seem to offer any advantages over Desmo drive, and it's certainly clunky! Really don't think the 'valve pistons' could offer the same gas tight seal as conventional poppet valves. There's also a helluva lot more reciprocating weight, but my main question is.... what the hell's going on with that combustion chamber!! It's just basically an opposed piston engine, but without the advantage of being able to take drive off the second crank.
If there were to be a new 4-stroke, sleeve valves would be the way to go in my book. Fairly common in aeronautical engines in the 20s-30s. Port area can be as big as you like, no chance of collision, and much more compact.
Michael