I think it's a solid choice and I'm waiting now to see what Capaldi is actually like in the role, because he's been in so many different things and shown such variety that I don't think it's possible to say at this stage. Even looking at his two Doctor Who-related parts in Fires of Pompeii and Torcwood: CofE shows the range he has and how he's equally good in comedic and more dramatic parts.
I wonder what it says that they've decided to pick a "name" actor (even if I wouldn't call him a household name even here in the UK) rather than a relative unknown, if indeed it says anything at all. I do think having an older Doctor is going to be interesting, and is long overdue - it opens up different possibilities and ways of doing things. Less running about in order to solve crises, I hope, and more thinking/talking his way out of trouble. Although for all I know Mr Capaldi is a fine physical specimen who can run and flail about as well as the younger guys.