This has frustrated me too. Unlike JSR (and quite like Zineth) the air movement code only allows you to redirect existing velocity, not add any. I did it on purpose so you can't jump your way past your character's top speed; this is a side-effect. I'll try to allow adding velocity at low speeds to mitigate the frustration.
edit: Done (not upped), and you're right, it feels much better. I've put the falloff at exactly one-half of the speed cap.
2dit: Upped.