I loved the characters and the story quests. Walks-Softly quickly became my favourite out of all of them. I had a lot of fun running around trying to complete Kari's Hit List, and the daily heist quests are pure adrenaline. The tip board quests get a little repetitive seeing as there are only five of them that circle round. The daily requisition quests are worth going for, especially if you're a crafter. The requisition areas are usually around the world bosses, and these ones don't kid around like the ones in the base game - you can't defeat these ones on your own (unless you have an extremely OP build and can one-shot boss enemies of your own lvl). But the bosses almost always drop a part from the Outlaw crafting style. No need to worry, though, as there are plenty of people around in the DLC zones (it actually gets crowded, which rarely happens outside the starting zones in the base game - now I know where all veteran leveled players went). All you need to do is shout in the zone chat and people will show up. Maybe they have a requisition quest, or maybe they're just farming the crafting style or the XP. Doesn't matter, they'll get there.
The main quest proved to be both gut-wrenching and heart-warming and I really enjoyed it. The personal quests of the characters were also really amazing and I kept coming back to do tip board quests so that I could lvl up my Thieves Guild rep and help my new friends some more.
The only thing I haven't done in this DLC is the Maw of Lorkhaj, a new Trial, which is a 12-person group dungeon basically. I don't know enough people to fill a group and it's too much trouble to find 12 random people :P
But apart from a few hiccups in the beginning this DLC was amazing. I loved it, and I actually missed it when I finally moved on to Orsinium.
But back to the story, it wasn't until the second half of the main quest line that I started to become invested in it, and after that it was mostly because I completely adored the Bosmer part-time companion Eveli Sharp-Arrow :3 Towards the end of the quest line came a plot twist that I really didn't expect and that helped making me invested in the DLC. The accompaniment of Eveli and the final heartbreaking quest of the main quest line helped this DLC immensly.
Orsinium also has a thing like Kari's Hit List where you collect artifacts for the House of Orsimer Glories, and that was fun once again :P The DLC also includes daily delve quests, where you go inside a delve and complete it and bring a quest specific item back with you. Since I basically explored the whole map before I even found the daily delves, I didn't really bother with them. I'm not a fan of going through a place again that I've already been just recently.
You got to reencounter a few people from the previous base game zones in Orsinium, which was a lot of fun - like Kireth & Raynor Vanos and Rigurt the Brash who were all throughout the Ebonheart zones, and Skordo the Knife and Lady Laurent from the Daggerfall zones.
As of this post, the only things I haven't done in Wrothgar (the Orsinium DLC zone) are the two public dungeons and the Maelstrom Arena. I've gone halfway through the Arena and it went well enough (apart from my over-consumption of health potions), and I'm planning to do the pub. dungeons with a friend at some point or other so that will change.
I probably have a worse opinion on Orsinium because I never liked Orcs or the Forsworn, while I loved the Thieves Guild in both Oblivion and Skyrim. So my heart was in it from the beginning with Thieves Guild DLC, while my interest was really low for Orsinium.