The Carnes arm here has some previous entries, check them out.
Now, Mark actually visited the man that sold him the Carnes arm 'over Internet connection and friends' (Mark: anytime again : ) Turns out things are now really going in the right direction.
Particularly for transhumeral amputees, I believe the Carnes arm has a lot going for it, but it definitely needs a tune up both in terms of materials and ease of clockwork. With osseointegration, you want light weight and as much integrated function as ever possible. Combining elbow flexion and supination is one really good example of a possibly sensible integration over several joints.
As far as I am aware, even combined hand and wrist motion, leave alone hand - wrist - elbow combinations, are really nothing our current commercial consumer product designers do consider in their current "all things are called now 'bionic'" rage. So as every now and so often, amputees have to look out for themselves.
It really appears that the Carnes arm re-engineering now is underway as I read this hot off the press news. Great stuff.