Nice balance on the shooting speed / distance and rotation speed, keeps you always thinking you wish you had _just a little more_ LOL
I can totally see having different upgrades to purchase as you advance through the zones, maybe multiple ships at different angles, moving in opposite directions or different speeds so focusing on one makes you lose track of the other and you can't really control both at once effectively. Keep the "edge of frustration" feel.
And I agree with everybody else, killer title screen effect