He is a fine actor in the right role, it has all ready been mentioned he is to perform Hamlet at Stratford, which has me worried, cos his Romeo was well frankly a load of old pants, BUT in the Comedy of Errors, he was great.
Maybe he has a talent for certain roles and not others, the thing with the Doctor is the actor makes the role his own, just by being cast as the doctor.
If some think him a gurning hyper active fruitcake, then that incarnation of the doctor is a gurning hyper active fruitcake.
In some respects it is a win win situation for the actor chosen.