I am posting this in resopnse to my message about a problem I had with set driven key and blend shape sliders. Needless to say, I realized (with much embarrassment) what the solution was.

First, the problem: I would set up a SDK relationship, but the animation would "snap" to the final keyed position rather than transition smoothly.

The problem was that I had set my animation curve preferences to "stepped tangents" rather than "clamped tangents". The (all too simple) solution is either to change your default settings to "clamped", or else go into the graph editor and change all the curves affected by your set driven key relationship to clamped tangents! :-)

I'm so proud of myself I think I'll finish my project with a paper bag over my head! :-)

Again, a caveat...check your animation curve defaults! :-)

Carry on smartly...!