I have one (non HP model). EFI is great. Here are a few problems to consider....
1. Throttle body will need rebuilt periodically. Might be a good idea to have a spare to swap while the other is rebuilt.
2. Computer may need reflashed periodically. I went through two after 1100 hours. Haven't had any problems since then. Again, might be a good idea to have a spare to swap in case any problems do arise.
That's about it. Otherwise, you'll have a strong, mostly reliable machine. Here's a list of other spare parts I would keep available to avoid down time:
1. Complete set of belts. We replace every two years
2. Spare switches. They do go out from time to time.
3. If it comes with an APO (automatic pump out), have a few diaphragms on hand.
4. Tune up parts. It will need tuned up every two years (plugs, cap, wires, air filter).