Steven Moffat sat down with Doctor Who Magazine and elaborated more on the personality of "new" Doctor Peter Capaldi. In it he said not to expect the brilliant, good boyfriend types that David Tennant and Matt Smith had portrayed, but something a little more mad (I'm guessing UK slang for crazy), dangerous, and difficult. His full statement can be read below.
Well I'm certainly glad there isn't going to be any sexual tension between the new doctor and Clara Oswald, that would get strange, but I do like the change in personality as well. He also said characters like Madame Vastra, her lover Jenny, and the idiotic but lovable Saturian Strax will be appearing in the first episode and that it will be strange indeed when they meet the new doctor! Cool to see them back, but I was pretty sure they died on Trenzalore... I wish someone would explain this. my timeline of what has and hasn't happened is all screwed up.