These engines caught my eye on this side of the pond as well. According to their spec sheets fuel consumption over the useful range of the engine is about 3.8 lbs per horsepower hour. This is fairly typical for modern turbo diesel engines. Electronic control and variable turbo should allow a broader load range as well, but it also adds complexity in that you will be a slave to the dealer if anything goes wrong. I tried to get specific answers from Hyundai and our nearest dealer with respect to maximum and minimum continuous loading specs as well as expected life under different conditions. All I got was vague answers or no answers at all.
As attractive as they look on the surface I wouldn't feel comfortable committing to one without some more proven case histories.
1993 Bayliner 3288, 351 Fords, converted to tuned port programmable EFI. 2012 AB 9.5AL RIB, Yamaha 15MSH (tender)