So, Catherine Tate is returning as Donna as The Doctor's companion for all of S4. I didn't mind her. I didn't love her. I may or may not watch at all. It depends how I'm feeling at the time.
My reaction to this is to fondly think about how awesome it could have been to have some episodes with The Master as The Doctor's companion. Just one or two, you know? It would have been like The Odd Couple, only with more genocide.