1)According to our Russell on one of the extras, this was meant to be this season's "cheap" episode. If so,, then I think they did a good job covering it up.
2)The "Previously" part kind of gives away who the baddie is going to be in this one. Perhaps it wasn't that much of a concern for them. For that matter, the "Next Time" at the end gives up who the baddies will be next episode.
3)"Six months later" - would it be possible for someone to become mayor of Cardiff that quickly?
4)Blon/Margaret is a good villain in this one. I tihnk it deomnstrates that one baddie can be an individual, groups of them tend to turn into faceless hordes. She does her best to play Team TARDIS with lines like "You're very quick to soak your hands in my blood" and "You butchered my family and ran for the starts, am right?"
5)Good interaction between Margaret and the Doctor as well: "This is persecution. What did I ever do to you?" "You tried to kill me and destroy this entire planet." "Apart from that."
"I don't make the law." "But you deliver it."
as well as "Only a killer would know that" and of course, "Dinner and bondage. Works for me."
6)I like dthe confrontation betwene Rose and Mickey. At the time, I thought that this might be the last we saw of Mickey. It would have been a good scene for him to go out on.
7)"Venom Grubs" a callback to "The Web Planet"!
8)And of course, they finally draw attention to the whole "Bad Wolf" thing. Can't say as I'm wild about every season having an overarching theme. You'd think the Doctor would start to notice that after awhile: "That's the third planet in a row where we've met someone wearing a Bengals jersey. Hmmm...Guess we've got a 'football' theme this time."
9)Is this the first time they've used the Rift for fuel?
10)Some fun quotes:
Overall: I enjoyed this more than I remembered. the Slitheen aren't my favorite heels, but Margaret/Blon by herself was an interesting character. I found it interesting the way the show took time to explore the moral issues.