I have most of the stuff that has been put out for Hunter so far, and this would come right after the Survival Guide in order of usefulness and game expansion. The Hermit class is EXTREMELY interesting (they hear voices from the Messengers constantly) and the Merits/Flaws really help to round out a character (there's a fair bit more than just the standard merits/flaws that find their way into all the player's guides).

The roleplaying tips and ideas are realy nice, especially concerning what types of people are likely to pick up a given creed. There are some interesting rules presented on changing creeds as well (you were an innocent, but you've seen enough, etc.) which make good sense. A whole section on Bystanders is a nice addition as well (they hint that many Bystanders are failed Hunters - ones who heard the call but failed to act).

There's more here than I can lay down, suffice it to say if you've picked up the main book and want to delve deeper into the roleplaying of Hunter this is definetly a worthwhile purchase.