Flash has totally binned it's armature animation stuff, or at least changed it enough that I can't open those files again without it all being turned into keyframes, but the hair was actually done with a different kind of 'bone', that let you do arbitrary transformations on the whole shape rather than splitting into parts. (Also minor touch up in photoshop).

I had a lot of trouble trying to do it split into separate bones, too. It looked okay, but a lot of gaps appearing at certain angles no matter how careful I was with the shapes at the pivot points.
The popping in / out looks weird because it's stopping everything where the motion should be fastest. It's hard to explain without a graph or examples, but instead of slow-fast-slow (spread out however you like, style-wise) for the whole movement, you have it for every pose, even though the extreme pose should be right in the middle (fast part) of the arc. (Maybe someone else can explain this better)

Keep it up though!