Nice to see everyone else's ideas.
1) Publishing
2) Fix codes and release in a large patch
3) Everyone's happy
4) Play endlessly
5) If something is wrong: Another patch
Simple as that.
No, for real:
1) *historical* Realism (since it is a sim)
2) Feeling that the creators put in all effort for creating this game
3) *historical* Flight models and landscape recreation
4) Framerate
5) Sound
And then it's time to see some mods, just like 1946
MugiSNK