In general I'm very happy with the sounds ingame. I love it to hear the other planes taxiing and starting while my canopy is open.
What worries me the most in terms of sounds is the lack of drone/deeper tune and loudness of the two-engine aircrafts, especially the bombers. As I've stated this in a seperate thread before they are just waaay to quiet.
Sometimes allmost impossible to hear even in a bigger formation of them