For a comedy, I found this episode quite heartbreaking. It's kind of the culmination of every episode that preceded it. Donna, finally acknowledges her feelings for Karl, only for him to take off before he hears them, Louise can't quite come to terms with her insecurities and Karen's storyline is the most heartbreaking of all. She finally puts her faith in Billy only for him to let her down.
There are funny parts to this episode, Donna's date with someone she meets on the bus etc, but it is mostly about the development of the characters. It's quite moving when Karen finally decides she might be ready to start a family, only to have that dream snatched away from her within hours.
It is a good cliffhanger, which makes me want to see what happens, especially with Donna and Karl, even though I don't think they''re suited at all! Roll on the next series.