My commute time today was long enough that I got through the whole series/season/whatever.
It's okay. It's not as outright hilarious as the earlier series/seasons, nor as consistently funny. The really funny moments are fewer and farther between. Karl completely disappears for a while in the third episode, leaving Ricky and Steve to talk amongst themselves for ten minutes or so.
I liked it better when it was in true, clear-cut episodes. It seemed kind of odd that Episode One ended, and Episode Two began with them picking up the discussion that they were having at the end of Episode One. There didn't actually need to be an episode break, except for the fact that about half an hour had passed since the start.
I won't spoil anything by transcribing or repeating the best jokes. I'll just say that the stuff about the Nazis was probably a little too serious overall, but the best parts were probably (a) the "Room 102" discussion and (b) the "Desert Island Discs" discussion. The gay marriage bit in the first episode was okay, but not quite as good as the stuff that followed.
It's probably the weakest link in the chain of five. But, on the whole, it's still funny, it's still worth a listen.