I just recently ran this for my group, and the adventure simply is... not good. It's not terrible, but there are too many better adventures out there for this to be rated anything more than 2 stars (the higher starred reviews are, AFAIC, inexplicable - I sob to think what people have played through in the past!). ;)
There are numerous editing errors and omissions throughout, including a missing key, no mention of where a passage goes to, and no note of what the doors are made of. Encounters are of a questionable nature (CR 3 shadow in a room with a necessary key immediately comes to mind) in difficulty (especially when it is discovered that there's pretty much a time limit involved).
Notable is that the maps are truly horrendous. It looks like it's just a bunch of ugly, simple tiles put together (which it is), and the boring layout and ugly map quality result shows. Really awful - my players rolled their eyes seeing the layout and maps (especially disappointing considering other Paizo products... including part 2 and 3 of this series!).
The story/motivation is decent (and if explained well enough by the DM, I've found is good enough for players to want to continue on to the next modules in the series - though I tied it into our FR campaign, which we prefer, so that helped a lot I think), and the town of Kassen (complete with a nice map and good description) was really great and added value.