I enjoyed it a lot! Proof:
Last stage was very hard! :D
I reminded me to the parrot mechanic in Dokey Kong Land 2 (I loved the parrot stages).
The levels got more and more interesting as you progressed and IMHO it was clever to reuse some level and adding new things, like the wind.
And I also liked the sound effects. In fact, that tiny details is possibly one of the things that keep me engaged and willing to complete it (it was nice to feel the feedback when you beat the wings).
At the beggining, I was trying to avoid that... flies (?) you had to recollect, I thought they were harmful. Maybe adding a more appealing colour would help.
But its a minor thing. Good job!