I really enjoyed Omega. I think, as a complete package, it's one of the better flowing, long, and satisfying combat arcs in the series. The encounters are a lot of fun and Montreal did a better job of avoiding LOCK IN ROOM, FIGHT WAVES with Omega than they did (alongside Edmonton) with ME3. A lot of the encounters are relatively short lived when it comes to backup waves, there's mini one/two guy encounters down halls, and so the pacing feels surprisingly fast and less rigidly designed compared to ME3. Like it kinda just embraces the shoot-bang and does a great job with it.
On the downside the story is a total hit and miss depending on how much you like Aria, as well as Omega given the context of ME3's plot arc. I actually think there's a lot of good stuff there, if typically cheesy, but it's the kind of story arc that just doesn't feel right within ME3's framework, and isn't long enough to build on its ideas (like the new character). The ending suffers because of this, a pretty dumb character moment which has little impact on the player as the compact mission length fails to build attachment and exposition for said character.
But I digress. I was a wee bit disappointed when I first played it, for the latter reasons and because it is/was super overpriced relative to other DLC and the stupid, insane promises/hype BioWare dumped on the pack leading up to launch. But on my last playthrough I appreciated it a lot more. It's a strong arc, has some great encounters, and I'd say is one of the better gameplay/shooter paced missions in the series.
