1)In this story we get the re-invention for the new series of the Silurians, creatures first seen back int he 1970's. I can't say as I was perfectly happy with the new version of these critters - I accept that they had to be "modernized" a bit - the old versions were a little to much obviously "guys in rubber suits". However, I think I would've preferred it they had stuck a little closer to the original verisons than they ultimately did. Still, the story itself followed the usual pattern of "Silurian" adventures, with the Doctor once again trying and failing to make peace between humans and reptiles. At least the Silurians didn't all end up dead this time. I liked the "Eocene" gag, that's one of those bits where you have to be familair with the old show to get. The scenes with people being pulled into the ground were well-done, I thought.
2)The other big development in this story was Rory's second "death" - so really good emotional stuff where Amy desperately trying to remember, and the Doctor's anguish when he realizes that she's forgotten Rory. This is compounded by the reappearance of the crack in time and the bit of roasted TARDIS that the Doctor pulled through it.
3)Cliffhanger for "The Hungry Earth": The Doctor and Nasreen find a Silurian city underground! Resolution: It turns out they're all mostly still asleep.
4)Some fun quotes:
Not bad - I've always enjoyed the Silurian stories because they make me think about what the moral issue as regards what accommodation the humans and Silurians ought to make for one another - since neither is "wrong" from their own points of view. I would like to see them someday do a story which ends well, with the humans and SIlurians learning to live with one another.
[Part of list of Doctor Who episodes here.]