I've been doing some lip/mouth movements using switch layers and HeyVern's trick with using interpolation, making a keyframe and dragging the inner switch layer out of the switch layer.
If you're real careful about not adding points or peaking them, the interpolation of the layers can really make things smooth. In my mouth layer (inside the switch layer) there's a filled group for the lips, teeth, tongue and inner mouth. I make sure that auto-weld is off (the space bar is how I weld things now), so I can move points around with ease. I make sure that I name each of the groups so I can acess them if they are hard to manually select.
I've read Stop Staring, and even though it's for Maya/3D programs, the sections about mouth shapes has given me ideas that all I need is to make the 9 basic "visimemes" (smile, narrow, frown, upper lip up, upperlip down, lower lip up, lowerlip down, tongue up, tongue out) and then in the switch layer do what Vern outlined in one of his tutorials (it's at
http://www.lowrestv.com/moho_stuff/swtichpointcopy.html). It's a bit labor intensive, but I think it's worth it, as the mouth expressions with point movement have a kind of consistent look and unity to them that bone movement just doesn't quite have.
One thought, maybe you could name all your mouth bones and then recreate the bone structure and then constrain the mouth bones to these control bones. On the ControlBones setup, you could also constrain the amount of rotation.
Hope I'm making some kind of sense. The good kind.
Once I get over the issues I'm having with rigging my figure, I'll post a quick render animation ofmy character's mouth shapes/expressions.
hth