He's not the most immediately exciting choice they could have made, but I'm willing to give it a go.
There's no question there's ben a general progression to skew younger and younger as the years have gone on. I would have been tickled if they'd bounced back to up to someone of Nighy's age, but perhaps there's something to the age of the new Doctor in what Moffat's got planned storywise.
Regardless, THAT is the new keystone element for me. If Moffat can handle the show half as well as he writes his individual episodes, we're in for an interesting ride.