What is great with every doctor since William Hartnell, is the distinct personality mixed with a little of what has come before. Sometime it works. Sylvester McCoy developed the sly yet wise old traits of the First Doctor in his later stories, to brilliant effect. (Think of his manipulation of Ace in their final series). But then Colin Baker also took on traits from Hartnell, most notably his gruffness and arroganceand came off poorly as a result. Hes frankly horrible to Peri and that make it difficult for the audience to relate to him. Matt Smith is a perfect blend of old Doctors mixed with his own. The childlike, inquisitiveness of Troughtons second Doctor. The energy of Tennants Tenth. The slyness of McCoys Seventh and the grandeur and dress sense of Paul McGanns one and only performance as the Eighth. Theres even a bit of the eagerness of Tom Bakers Fourth and the whiff of arrogance of Pertwees Third Doctor. But none of these traits threaten to overpower his performance. What it does is make it believable that the Eleventh has the traits and memories of all his previous incarnations.