So far Capaldi seems like a good choice, but I am mostly concerned about the writing. Moffat was great as an episode writer, but he has his weaknesses as a showrunner.
One big issue is that I don't think the gets the balance between between build-up and payoff right. I know that it was never a good idea to think too hard about the resolutions of Doctor Who stories and that usually they still work as character moments. However I think often he is trying to be too clever for his own good, resulting in episodes that don't stand on their own very well but only work as part of an elaborate build-up to something that unravels in the end.
The other is his overuse of informed-cool Poochie characters like River Song and especially Vastra.
Of course I still can't wait to see the new episodes.