The setup to this is interesting, and some of the encounters early in the adventure could be cannibalized, but Illefarn itself is disappointing. It's a great sprawling dungeon with three factions fighting for dominance, but these factions are not given good motivations. They all amount to "there's good loot here, yo!" but none of them except maybe the dwarves are trying very hard to find the loot. Aside from the story, the dungeon is also hard to prep and dull many rooms in the dungeon are completely empty, some are lacking descriptions entirely and the maps are confusingly laid out and hard to read. How the different floors connect is not immediately apparent, so you spend a lot of time squinting at the map for this floor, going back to the side-on diagram that shows how the staircases connect, and then trying to find the room it connects to on a third page. Sometimes these things don't even line up and you just need to find the correct answer by process of elimination.

And then you get to the bottom and you solve the great problem of the poisoned river by literally pulling a lever that dumps a bunch of poison in the river.

Only pick up if you are really in love with the idea of your players starting as City Watch in a little border town or have a cool idea for a three-way struggle in an old dwarven ruin between Orcs, Necromancers, and Dwarves, and don't mind spending a lot of time frowning at old maps to make that idea come to life.