The in medias res beginning worked very well for this episode, and I'm quite liking David Tennant as The Doctor. His performance tonight was suggestive of Doctor Eight's childlike joy at finding a pair of shoes that really fit.
Mind you, if Elizabeth Sladen was willing, I'd be all over Sarah Jane becoming a regular again. What a gal! But this is good too. :) I get the impression that, having won over "the general audience" with the first season, Davies is now trying to win over the Who fans who didn't like way the first season made a point of disassociating itself from the past. "Look!" he's saying. "Here's Sarah Jane! Here's K-9! Here's the middle eight bridge back in the closing credits!  It's the Doctor, the good old Doctor, really!"
To me, that's a Very Good Thing. :) I never once wanted a "hip, new Doctor" -- I wanted my silly old Doctor with modern production values!
 Not detectable on the SciFi channel 'cause they murder the credits, damn them, but I've seen the closing credit sequence on YouTube.
PS: Thanks for the birthday wishes, everybody! ^.^ I've had a terrific day.
PPS: Yes, I know Sarah Jane is getting a new series on her own, sans K-9. She would have gotten a series last time except the BBC likes to shoot itself in the foot. :P