Feel free to watch a quick facial rig demo.
[VIMEO]85712049[/VIMEO]
Overall a good start.
Some thoughts.
If you are going to arbitrailly pull controls around make sure you know you are going to poses that show good deformation.
The the quality of that model is high but the deformation is not a the same level. When pulling the controls around for the mouth you are getting into some combinations that are breaking down. For instance, at 0:28 when you pull the lower lip up and the valleys are happening near the corners of the mouth because the lip is jutting out strangely. I would set up a corrective combination system if you haven’t already.
The nasolabial fold should be showing up more when the mouth corners go up and when the mouth widens. There isn’t much of a feeling of the muscle bulging and the skin folding in this area.
The outer brow also feels off when you are pull the brows up because of the valley showing up (0:23). The brow winkles could be showing up more also.
When your character looks to his right you are getting some strange bulging in his left eye. (0:28)
Honestly the deformation in the last part with the muscles is not working in the mouth. The corners of the mouth are bulging for no apparent reason when they should be getting thinner as the mouth opens. The valley beneath his lip corners is getting very deep and the nasolabial fold is softening. The muscle you have for his right mouth corner is pushing the skin out near the jaw bone making it look like another bone is there(0:55). I like the skin sliding affect you are getting with the jaw.