So, impressions! I played for about 3 hours last night. It kinda feels like I've done the bulk of the main story and am approaching the end, but I'm not sure, and I've unlocked 0/4 achievements so far, so there's obviously more to do. My impression is definitely positive, and it felt in some ways like they're taking the opportunity in DLC to correct deficiencies with the main game.
One thing that bothered me a bit about Inquisition was that the main story quests felt disconnected from the world. Any time you were doing something substantial, you were in an instanced, linear 'setpiece zone' that you only visited once, and the only things to do in the actual open world were 'kill 10 dickwolves' sorts of quests. In Jaws of Hakkon, the story quests have you traipsing around the open world, doing stuff in it. That felt good. The new Frostback Basin setting is great-- big and varied, without being too big. It's dense with interesting locales to see, with some interesting verticality going on too.
One very cool thing, is that at the beginning of the DLC, you're kind of presented with two possible avenues of progress-- speaking to a scholar in your camp, or seeking out a friendly native tribe and speaking to their leader. I opted to go see the tribe first, and did a quest or two for them, and when I looped back to the scholar, my dialogue with him reflected everything I had already learned from investigating the tribe. Very nice.
I did hear a lot of intra-party banter, but I don't recall anything that sounded specific to the DLC setting; I think it was probably all stuff leftover from the main game that I just hadn't heard yet. Party members do individually comment on stuff going on in the DLC quests though.
I feel like there's less loot in Jaws, but it's better stuff. I've only found 4 or 5 new weapons, but 2 of those were substantial upgrades to stuff my party was carrying. I like that kind of setup better than feeling like I'm drowning in vendor trash. Also, it's not part of the DLC itself, but oh my god that storage chest was needed. The first thing I did was dump 90% of what I was carrying into it. It was so nice, when you've only got 90 inventory slots, to not have to carry around dozens of runes and weapon parts in case I needed them later. Instead, I found a weapon with an open rune slot, warped back to Skyhold, browsed through the runes in my storage chest, did the modification, and warped right back to what I was doing. No constant micromanaging of my inventory, because I have 10/90 slots full instead of 85/90.
Scout Harding! Great to see so much more of her in this DLC. Seemingly no new romance opportunity, but that might be because I was already attached to Cassandra.

Hear our demand BioWare, Harding romance or riot.