Wamdue, you do understand that Doctor Who isn't the cultural institution in the United States that it is over there in Blighty? That Doctor Who is a niche science-fiction series on a cable channel that not everyone gets and is watched by a dedicated adult audience? That Doctor Who isn't "family viewing," but instead it's firmly in the science fiction ghetto?It is better than nothing, it just does not seem like that bigger deal, when the show is on past midnight.
You may say to yourself, "But that's not who Doctor Who is for," but that's who it is for over here. For an American Whovian, having Matt Smith on an American late night talk show is huge. Doctor Who has escaped, even if it's just for an hour, from the ghetto.
I'm not trying to oversell Craig Ferguson, but this is arguably more important for Doctor Who's visibility over here than even the FOX television movie was fifteen years ago, because that movie was terrifically easy to pigeonhole into the science-fiction ghetto. This is a late night talk show. There's nothing pigeonholing about that.