I've already mentioned the 2009 Christmas Special in the "Doctor Who Specials" post, so let's move on to 2010, and Series 5.
New Doctor, new head writer, new companion, new production team, and overall pretty much new look, Series 5 runs from the 3rd of April to the 26th of June, and just a cursory glance at the graph above shows us one very obvious change - the gap between the Overnights and Finals is noticeably larger.
It's almost as if something has happened to change Television overnight. The average Timeshift in 2010 is now a whopping 20%, and in some individual cases more ("The Hungry Earth" sees a Timeshift of 30%). It is tempting to see this as a direct result of SKY's policy to offer the SKY+ HD box as standard from January 2010 onwards, and to be honest (fan arguments notwithstanding) this is the most likely cause. Whatever the reason 2 out of every 10 viewers seem happy to record Doctor Who and watch it later.
As far as the individual ratings go, the peak figures of the Specials year have not been maintained, and Doctor Who has settled back into a familiar 6-8 million range. Gone are the glory days of the Daleks boosting ratings, and Fans (and the media) have tried to spin this series as a ratings decline (especially with the obvious drop in Overnight viewers), but it is becoming increasingly apparent that 6-8 million is Doctor Who's core viewership. Combined with continuingly healthy AI figures, this indicates that Doctor Who is a very successful TV show indeed.