Disclosure: Like the first reviewer, I too have a contribution in this issue of Wayfinder.
I am running Carrion Crown right now, so I've had Ustalav on the brain and was eagerly awaiting this issue. I was wicked pleased! I could go through every single entry and find lots of great things to say, but such a thorough review would (as they say) take years and cost millions of lives. I'll just pick out a few things for time's sake, but know, contributors, if I didn't mention your entry specifically, it is still awesome.
Artwork
Wow. Just... wow. The look and feel of this is outstanding. From the cover art (love the Grinning Moons lurking in the Pharasmin stained glass) to the individual pieces, the whole thing evoked Ustalav. A few of the pieces I even wanted in poster form (am looking at dodeqaa's creepy skip-rope Ustalav girls... shudder)
New Rules/Mechanics
I can't believe the Lycanthrope bloodline isn't already a thing. That's how good an idea it was, and it was really well executed. This needs to be an official thing, seriously.
Likewise the archetypes. I'm a big fan of witches, and the Geist Warden is a great character option, while the Afflicted is on my list of villains-to-be (a disease for a familiar! Only in Ustalav!) The Operatic Duelist is a great option for the prima donna (in a good way) swashbuckler at the table. It ain't over till the Operatic Duelist stabs, as they say...
Speaking of opera, I loved the idea of bardic masterpieces dedicated to the Old Ones cults. Of course a pleasant evening at the theatre in Ustalav would wind up driving one mad with the power of Hastur!
Items
The Folk Charms of Ustalav are great low-cost items that fit the flavor of the country very well. I'm a sucker for superstition-driven magic items, as well as options that lower level characters and common folk.
The Forbidden Tomes I also really enjoyed and look forward to placing here and there in hordes. Nothing like a good book to take you far away... far, far away to the unholy darkness between the stars as it turns out... Muhahaha...
Lore, Stories
All three gazeeters were very useful and filled in some of the sketched out parts of the official canon nicely. It is going to be hard not to find reasons to alter the Carrion Crown AP to make the party go to Kavapesta, Ardagh, or Chastel, if only to look around and learn more about the world as presented by those writers...
Side Quests and the Rest
Forgive me contributors all, for cutting this review short and not individually praising every one of you. Sadly, I have not yet discovered the secret to lichdom and therefore time presses on...
Suffice it to say, for those of you considering downloading this product, the side quests are a great way to bump XP during Carrion Crown or just to give your players some wicked creepy thrills in the Immortal Principality. And if you're looking for inspirational, fun reads, the fiction is spot on.
All in all, an excellent issue!