I have separate bindings for aiming. Shift and spacebar feels by far the most natural for me.
As far as streamers go, DrDisrepect uses forward and back on the mouse, Shroud used Q and E. Although Shroud never takes his fingers off the A and D, he says he twists his wrist to have his middle finger hit Q and E. I could see the benifit, but its super weird to get used to.