Well, I watched
The Christmas Invasion on Christmas Day, and it wasn't half bad. Tennant made a good start to his tenure as the Doctor although it was a bit tricky to gauge because...
*spoiler*
...he spent much of the episode in a post-regeneration coma (and a rather natty set of pyjamas!), leaving much of the episode to Rose to do the world-saving.
Based on what we saw of him though, he looks a very promising Doctor. He gave a very assured performance wide-eyed one moment, darker and almost menacing the next.
The special was pretty popular with the viewing public too, peaking at 9.8 million viewers second only to EastEnders in the annual TV Christmas ratings
battle.