This game is super fun!! I really liked the upgrades that were there, though admittedly I didn't really feel the burn with some of them -- for example the extra jump was immensely helpful even though I barely noticed the lack of air control.
That being said, the upgrades are still well done and make sense, and more importantly the game itself is super fun. The player feels really good to control, and every action you can take just has so much umph. The game itself is incredibly well-done.
My only real complaint is that the boss design felt somewhat lacking up until there were multiple bosses per round.