Riff,
Don't think it's the same engine, looks like a Mercedes derived aero engine(?). I'm impressed that the flight test is in a YAK-52: Those wings are relatively untwisted, which means it will be capable of flick rolls (spin entry under gee loading from say a 60' bank with tip stall that washout is normally there to reduce) so that first flight was just a gentle look-see. When you consider the problems that Thielert had with the gearbox before handing the concern on to become Austro AE4, you'll understand what I mean. That prop will generate impressive gyroscopic torques. Being a V12 should help keep crankshaft torsional vibration down, but it would not suprise me if TV was why TEOS/Airbus picked a V8 for Ironbird.
Gemini,
What you say is all true: AvTur diesel can never hope to match turbine for power-to-weight. But the benefit is that you do not have to rely on exotic materials, coatings or casting processes like you need with turbine first stages. This translates to reduced operating costs because overhauls can be less extensive, which combined with the fuel burn then reduces costs-per-hour. The RR300 developed from RR250 for the R66 was specifically designed to remove axial stages for reduced overhaul costs. The next step is to consider combining piston high pressure stage with turbine low pressure stage to get the best of all worlds: low weight, low cost, good efficiency...