Goddamn is this DLC good! I felt like the areas of the main game really hit or miss, (as good as Ithryll and Lothric castle are, there are some really aweful areas too, like Ithryll dungeon and Smoldering lake). The beauty and complexity of Ariendel however is just amazing. There are a lot of diverse enemies, really great weapons and great level design. Although the base game was relatively linear, Ariendel has more of that dark souls 1 vibe of looping around in the area, expanding it, and unlocking shortcuts. It also has A few really interesting optional areas with some pretty tough enemies in combat encounters. Definetly take some extra time to look around the area. Although you can blaze to it in like 3-4 hours, and many people criticize it for being short, There are more optional areas that some-what make up for it.
(Spoiler-ish section, I talk about the bosses)
Personally, I'm a huge fan of the two bosses they added. There's one optional bus that many people don't like, but I found him to be a cool change of pace and a fun encounter with an interesting arena.
The final boss of this DLC see though, oh my god is it amazing! It has this way of ramping up difficulty while teaching you how to deal with its many faces throughout the fight. The visuals are incredible the challenge is fair yeah extremely high, (harder then anything in the base game, though that's pretty par for the course for dark souls DLC). Personally, The final boss for this DLC is my favorite in the series so far, And almost completely makes up for the lack of other bosses in this DLC. That being said, two bosses is not really that much, and I would've loved to see more, especially considering how good these two bosses were. But, quality over quantity as good, and the next DLC definitely didn't disappoint in the boss department.