Agree. FADEC is great, as long as it works. You can open and close the throttle at whim, don't have to worry about overboosting/overrevving, shock cooling, carbon deposits at idle, carb ice, leaning, whatever. Just set the %power and off you go.
I had never flown anything other than a fixed pitch prop before, and the only thing I really had to get used to was the fact that engine noise (pitch) is no longer related to the amount of power the engine is generating. You really need to look at the engine displays to know what's going on. If you've flown C/S props before this is probably not an issue, though.
BUT... What is really important to learn is the completely different failure modes a FADEC has, and what you can do about it. The Thielert has dual FADECs and you need to know how to test them, and how to switch from one to the other if that doesn't happen automatically. Also you need to know how exactly the dependency on the electric system works. Which buses are relevant, how to feed these from the (multiple!) batteries you have, and how long you can fly on battery power alone before the engine quits.
Oh, and there are no performance differences between Diesel and Jet-A. But with Diesel fuel the temperature limits for starting and take-off are a little tighter than with Jet-A. However that's only relevant at temperatures lower than -15C or so. In the DA-40 that I flew, certification for Diesel came later than the base certification for Jet-A. So there was a POH supplement for running on Diesel. If you grabbed a POH off the internet, you might be missing that supplement.