I just finished playing through this module, and we really enjoyed it. It's fairly open-ended and sandboxy, but still gives the players a good idea of what they need to do to accomplish their roles. It also makes good use of incorporating the Harrow Deck, and players who like props in their games will have fun searching the deck for the appropriate cards.
There's also a lot of room for roleplaying, considerably more than most pre-made modules I've been through. Almost every encounter has a fair amount of roleplaying that goes along with it, and many of them can be talked through with no fighting at all. Characters who focus on social skills will get a lot of use out of them. On the other hand, there's always a way to progress by picking fights, so groups that just want to hack things up will still have fun. There's a lot of variety in the encounters, and practically any type of character will have an opportunity to shine.
The way the combat encounters are set up is my largest complaint, though; the players typically have two or three days between each encounter, and most of them are against a single powerful enemy; or at least, if there are multiple enemies, there will be a boss and several smaller enemies that don't really matter. If the party has a character that is capable of going nova or if the boss just gets unlucky on a saving throw, the party may tear apart several of the "big" encounters in a single round. There are no smaller encounters to deplete the party's resources leading up to the big fights until you get to the very last part of the module.
A smaller complaint is that the plot hook is really completely irrelevant to the overall story. A random NPC gets sucked into this world and the players go in after him; he doesn't have anything to do with the story inside the realm, the players don't interact with him at all until the very end, and he really is almost literally just a hook to get the players involved. By the time our group was about halfway through the module, we had forgotten we were even looking for him.
Still, it's easy to recommend this module to pretty much anybody. It was a lot of fun.