In a word: Whee!
It's fun to fly around, dodge then shoot foes and even repairing yourself (because it's funny seeing your plane spin around).
Only nitpick is that it's too easy to cheese the levels: you can just hold trust to propel your self to where the last enemies are then repair while you wait for enemies; you can also shoot enemies from miles away, so levels are easy to beat without ever seeing every opponent.
For 'better difficulty' (make it a tad harder), I recommend that the player's bullets despawn when they are off the screen, so players have to hunt down their enemies rather than picking them off in the distance. Also, showing all red arrows (enemy indicators) simultaneously when there are a few enemies left would make them easier on the eye (rather than flickering between a few different arrows).