I've just finished the game after about 30 hours of gameplay. I'm going to briefly touch on what I liked and what I was disappointed by. This will be spoilerific, so be forewarned. 
 

The Good

1. The writing: Superb. Dialogue is sharp and witty. Characters are likable for the most part, and you're never embarrassed by what comes out of their mouths. (except when you're meant to of course)
2. The visuals: Much much better-looking than the original. Characters look better, spell effects are beautiful, and the art style is brilliant.
3. A lot to do: There's just a lot to do! quests, quests, and more quests.
4. The Characters: I know this is sort of covered by writing, but it bears repeating. The characters are wonderful. Te banter returns as one of the highlights of the game. I never get tired of listening to characters throw quips at each other while walking through the streets. I should also mention that the voice acting is excellent. Female Hawke now rivals Female Shepard for my favorite protagonist. No matter what options you pick, you always get a great performance. It's also important to note that he/she is a fully realized character in much the same way as Shepard. I much prefer a voiced protagonist that I direct in broad strokes to a list of dialogue options. I think the dialogue wheel fits perfectly into the Dragon Age formula.
5. The Combat: It's fun, fast, flashy. All those good f's. I'm sure many will find it divisive, but for me it's a welcome change to the DAO combat system.

The Bad

1. The Scope: This is the part where I clench my fists in frustration. The single biggest problem with this game is the scope. SPOILERS!! You spend the entire game in the city of Kirkwall. Yes that's right. Bioware: the masters of world building, confine you to a single locale. Now don't get me wrong: it's a well realized and detailed city. But honestly. If you had told me that the entirety of the sequel to a game that had you traversing dozens of wildly different locations would stick you in one place for 30+ hours, I'd have laughed you off of the internet. In fact, most of the problems with Dragon Age II stem from this one major design flaw as you will see in a minute.
2. Recycled Locations: This is truly baffling. At first I didn't really notice, but it becomes all too clear very quickly. There are only a few dungeons, and they get used over and over throughout the entire game. I'm not just talking about similar visuals, I mean they are exactly the same. Same layout, same locations. I am I truly expected to accept that the same hideout place I fought a bunch of smugglers in is also being used by a crazed Blood Mage, a cult, and a pirate? Lazy. Plain and simple, and not what I expect from Bioware.
3. Lack of a Camp: I know it seems silly to complain about this, but just hear me out. All of your characters have their own dwellings, and are assumed to stay there whenever not out adventuring with Hawke. It's an interesting approach, but it presents some problems. I suggest that the reason you feel so connected to characters in other Bioware games (your Mass Effects and DAO) is because they travel with you, far from their homes and yours. Confinement to the city allows for the characters to pursue careers and such, but it limits the sense of companionship you get from trundling across the countryside with your band of cohorts. It's also pretty jarring when you go to talk to them and they act like they haven't seen you in days when you've just spent the last 3 hours killing monsters with them. I know it's all part of it being a game and that all RPGs have similar issues, but it's harder to suspend disbelief in this case.
4. Lack of Urgency: Simply put, it doesn't feel like what you're doing really matters until the very end, and at that point it feels forced. It's hard to feel the consequences of your actions are really significant when the stakes are as low as one city's fate. When you've just come off of a game that had you saving an entire kingdom from a constantly-looming threat just on the horizon, it's a pretty big let-down.