I didn't play previous iterations of this campaign, so this is a fresh review. This first part of The Enemy Within is really good, forcing the characters to get involved in things that will reveal the nature of the threat that is Chaos to the Old World. Things can go really bad if the party doesn't complete the puzzle in time, but that doesn't involve an endgame scenario at all.
It fleshes out the city of Bogenhafen in ways only seen previously in this edition on the Starter Set (for the city of Ubersreik), and bundled with the Companion, it offers months of gameplay without even starting to get involved in the main plot.
[5 of 5 Stars!]