Beat it in a rushed play through in about twelve hours with all main quests completed. Didn't bother with the scanning garbage and skimped on a good number of side quests which I kind of regret. Really impressed with the dialogue, sound, and combat. The only major negative thing I kept seeing was that they had to wrap up this gigantically complicated plot they've created throughout three games in a single play-through and it shows how they sloppily mash everything into one coherent semi-related story line.
It also seems a lot less personal and deep for you and your crew members and characters you interact with. In ME2 you spent good portions of the game acquiring squad members, learning about them, befriending them, then earning their loyalty and that unlocked a lot of awesome quirky conversations and side quests. However in ME3, very few characters have deep sub plots and the majority of your companions have single line dialogue when you go to check up on them throughout the ship at different parts of the game. I probably added an hour to my play through just checking on the companions in every section seeing if they had any quests or anything I could do. But nope, just a few conversations here and there and you unlock their squad power. They did a really great job increasing the scale of whats at stake where you can see as an example, earth getting fucked up by reapers, but you lose a lot of unique interaction with your squad members.
Ill definitely play it again and I don't doubt that a lot of these things change if I were to do a much slower play through and focus on completion.