The Sliveen or however they are spelled are really the most irksomely boring villains ever. The return of them though in the episode about the Rift surfboard had a lot of nice acting in it and a decent plot. Certainly, lots of explanations of useful stuff (often clunky) and some amazing character insights.
And then there is The Game Station and The Parting of the Ways. These episodes upset me deeply, despite not being as good as The Empty Child arc. The Daleks are scary by the sheer virtue of speaking at the most aggravating pitch/tone in the universe. The Doctor asking the Dalek emperor if he would be his highest angel was downright chilling, but again leads me to ask -- what's with the Christian mythology in Doctor Who and hey, what's with the Gnosticism in SF/F in general (a source of endless fascination to me and a reminder that _someone_ needs to return my Milton to me)?
Anyway, my suppositions about Jack figuring out he is immortal (which apparently doesn't happen the way The Parting of the Ways left me thinking it happens) led me to annoy
redstapler with questions which led me to the Doctor Who wiki, which led me to the fairly common theory that Jack may be the Face of Boe which led me to writing melancholy Face of Boe fic.
In all these bad effects, clunky explanations and cheesy bits of humour there are some deeply, deeply strange, unsettling, sad and even slightly profound things going on. What a weird show.