I admire David Tennant. I thought he was fantabulous in Casanova. He's as good an actor as Ecclestone, but very different. I haven't adjusted yet.
I still say these episodes are too fast. The Big Bad is no sooner established than it's shot down in flames. I'd like to see more time allowed for world-building. More time for the very fine actors they've engaged to just mooch about and be touching and witty.
More time for suspense.
I understand the Beeb are prepared to offer Billie Piper all the Kingdoms of the Earth to stay on board.
As well they might!