..

I like the idea that there is more energy per pound in Jet A fuel than
AvGas, but I have no idea of the failure modes nor expected TBO and
other performance, operational, and maintenance issues. What should a
pilot expect to find has changed in the Thielert engine equipped C-172
other than higher power available at altitude, increased range, and
fewer refueling options?

The lower fuel burn comes not from the higher energy of Jet-A, but
rather from the higher compression ratio which converts a higher
percentage of the energy to useful work. Diesel comes closer to an
ideal Carnot cycle than gasoline.