That's an interesting point, Mark. Remember the second Martha episode - Shakespearean London, the Doctor and Martha get chased back to the TARDIS after a run-in with Lizzie? We never learnt what he'd done the first time to merit his chasing.
I was thinking of comments to make when I was watching the episode, and the fact that Donna is a lot older than Martha and Rose were was one I was going to make... but didn't. Both Rose and Martha were like girls. Donna is more a woman.
And something about the special effects - the Adipose looked brilliantly fatty. They were the right colour, and the light reflected off them perfectly. The second one in the big, purple woman's bathroom sink even slid around as if it were fat. I chuckled.
And the scene where Miss Foster lifted one out of her drawer was good - it was believable. The graphics moved as if she really was holding it.
The Doctor Who team must have a much bigger budget than Torchwood (whilst not bad, the TW CGI aren't really believable).