Aria T'Loak is back... for revenge!
Overlord tried to tell an original side-story in Mass Effect's universe, but didn't ... try hard enough; really, none of Mass Effect 2's DLCs felt like they "put in the effort." Omega shows what happens when DLC does put in the effort. (It's good!)
Omega introduces a new supporting character, a new villain, and a couple new enemies, but the real star of this chapter is certified badass Aria. Throughout the multi-phased mission to retake the Omega station from a Thrawn-like Cerberus mastermind, Shepard and Aria get plenty of one-on-one time, and Carrie-Anne Moss delivers her character's cutthroat personality so well.
Aria was already a great "bad girl" archetype, but this DLC gives her a chance to really shine, like an animal backed into a corner; left with no choice but to claw her way out.
I wish the villain was a little more present throughout the story, and I wish that the mission was a little less linear -- or at least didn't trap me on Omega inbetween phases. But that's a small sacrifice for this DLC chapter's tightly-scripted, well-paced, satisfying narrative.
Better than: Batman: Arkham City - Harley Quinn's Revenge, Borderlands 2: Captain Scarlett and Her Pirate's Booty, Mass Effect 3: From Ashes
Not as good as: Batman: Arkham Origins - Cold, Cold Heart, Borderlands 2: Tiny Tina's Assault on Dragon Keep
She may not be part of the Normandy crew: but this definitely feels like "Aria's loyalty mission."