I can understand trying to put a bit of a bank into the turns, but this game has a ridiculous autosteer which is confusing at best and often gets in the way of gameplay. Also the level of grinding needed is a little much for such a short game.
One suggestion I have is to make the nerd move higher in the screen when he gains altitude. It's a little weird and difficult to judge his vertical speed and position when he's always centered, then suddenly rockets out of the screen when he hits the 2k foot "ceiling." If he was near the bottom of the screen at 0', in the middle of the screen at 1k feet, and 75% up at 1.5k feet, I think it would look a lot better.
It'd be nice if behind solid objects like trees you could see an outline of yourself or an enemy. I've been killed a couple times by hidden enemies just because I couldn't tell where I needed to click!