[Spoiler (click to open)]The biggy is that Lena is apparently going to stay dead, unless someone else goes the metronome route, which is a shame because she was one of my favourite characters. The big plague problem is resolved, though opening up an exciting new can of worms which we don't know much about yet. James Marsters guest-stars as an antiquarian, and I suspect is going to become a recurring character, along with his nemesis. Deliberately keeping this vague since it really would spoil your fun if I said more.
On rozk's recommendation I also took a look at Defiance which I can best describe as Alien Nation crossed with Firefly - it's set after an abortive alien "terraforming" and colonisation attempt has devastated the Earth, and humans and a bunch of aliens of various races are trying to maintain some sort of vestige of civilisation in St. Louis, now renamed Defiance. They're basically doing it as a western, the setup for the first feature-length episode has the hero (a Man With No Name type with an adopted alien daughter) arriving in town just as a big crisis develops, screwing the local brothel keeper while apparently being attracted to the mayor (Julie Benz, aka Darla and Rita Morgan) too, and eventually providing part of the solution to the problem and leading the climactic fight against the