Well, that's the first of the two-story arcs finished, so what'm I left thinking?
As has been mentioned in other reviews, the plot does appear to fly past you at the speed of light sometimes. In this case, the fact that the main story [of the Slitheen takeover] finishes and leaves another 10 minutes of episode time to fill for character exposition, basically.
I wasn't impressed by the acting of Micky and Rose's Mum in the first episode, 'Rose', but it grew on me here, to the point where I tolerated both. Rose's mum still seems too overprotective - and especially at the end - very shallow. However, these remain minor faults in the scheme of things, and hopefully these characters won't return for a while, since Rose is now pretty much off with the Doctor for good.
The series continues along the 'moral' lines, with greed being the issue here, as in The End of the World. I don't have a problem with the show trying to be slightly more 'moral', especially since it's aired as a piece of family viewing.
I've noticed many complaints amongst previous episodes about the background music. I watched tonight's episode with this in mind, but I have to admit not finding any fault to it. It followed the norm - fast, upbeat drums during exciting bits, slow violins during emotional scenes - and yes, this is cliché, but there's nothing wrong with it.
Even more impressive are the computer generated effects in the episode. The BBC haven't skimped here at all, and everything from the missile flying through London [which reminded me of the beginning of the Bond film Tomorrow Never Dies] to the Slitheen giving chase looked impressive. I'd say the CGI Slitheen actually looked more impressive than their costumed counterparts, probably because in CGI there's none of the comical head-bobbing that happens when becostumed Slitheen try to run.
While I think about it, the episode title - World War Three - doesn't seem entirely accurate - there being very little war on a global scale involved, besides the UN allowing the UK to launch nuclear missiles.
I liked the fact that throughout the episode arc, the [original, dead] Prime Minister remained nameless, and even when the dead body fell out the cupboard, it looked sufficiently like the back of Tony Blair that the episode could easily have been set tomorrow, for all we might know.
The current series is going from strength to strength, and it looks like getting even better next week, when the Daleks return. The trailer was scintillating, anyways.