When I was a full time CFI in 2001, my flight school had an early
Katana with the 80hp Rotax & CS prop. I took an interest in the plane
(nobody else did - it was a ramp queen) and flew it probably 15-20
hours. While that is hardly enough time to make a truly informed
opinion about the engine, I've heard from A&P types that the 4 strokes
hold up quite well, even with their funky combination air/liquid
cooling. At 5gph in cruise @ 115kt (Katana) it's cheap to run as well.
The TBO was raised from 1200 to 1500 in 2003, and even though that's
still low compared to the typical 2000TBO for most NA Contis & Lycs I'm
guessing overhaul costs are proportional.