I would have made space shoot, too, incidentally (arrows + space should be the same for just about every keyboard out there), but configuration itself is a great idea.

I also wish that the length of time you held down the jump key controlled the height of your jump rather (up to a maximum, obviously), rather than one-size-fits-all jumps, but that's minor.

Play an old NES game that used that system like Super Mario Bros. (any of them) then play your game to see how much more in control you feel.