Movement: I would agree that rotation speed and overall speed are a bit much. It would be nice to be able to tap on an arrow key to rotate more slowly.
Strafing: sure, that would be easier, but I prefer the challenge. It is a pain in the areas with multiple turrets, though.
Rocks: do all rocks potentially grant powerups? I find it difficult to decide which rocks to waste bullets on. Which leads to..
Ammo: I like not having an absolute number, but find the display completely baffling. I'm never at 100% ammo, just somewhere vaguely inbetween. Is it 20%, or 80%? Too hard to tell. Or maybe I'm missing something.
Enemies: it might be nice if they don't fire at you when they are in a physically discontiguous area. There was one section, on the first level I believe, where if you got close to a wall, something on the other side would start firing. Since it's in a locked-off area, it seemed odd. (yes, many games do that, and it might be preferable to some people, but it seems weird to me).