The Shadow Broker DLC helps explain why Liara is different towards you in ME3. Much more reserved. In a way it's similar to Ashley but definitely more colored by Asari psychology. She's way more rational than Ashley. In a way almost everyone's opinion of Shepard is colored by the fact that he slept with the enemy, basically. Cerberus are big huge dickholes in ME3.
The Shadow Broker DLC was, in terms of consistency, even worse. Liara in ME2 is a completely different character from Liara in ME1, and the events described do not explain the change. Liara in ME3 so far seems reasonably consistent with Liara in ME1 - also, I boned her in ME 1 and now finally in ME 3 she's flirty again.
The Shadow Broker DLC was just stupid...eclipsed only by Arrival, which was kind of the worst thing ever.
Also, yes, I have played the first two games twice so I know what happened with Cerberus. And that's another thing I'd like to complain about. In ME 1, they're basically space nazis. In ME2, they're renegade puppy rescuers. In ME3, suddenly they're space nazis again. WHAT THE FUCK IS THAT. Yes, there were some mentions of the bad things they did in ME2, but they were completely glossed over and in ambient dialogue the crew would go on and on about what awesome people they were. I'm fine with having some moral ambiguity, but this isn't ambiguity, it's inconsistency. Everything they did in ME1 was horrible, then everything they did in ME2 was awesome, and now they're pure horrible again. It's inconsistent bullshit. The writers are just changing everything to fit the story they've cooked up, and I don't buy it at all. I thought it was already straining credulity in ME2, but now it's just ridiculous.
Meanwhile, by bringing back the unrestricted nonlinearity, they've removed any sense of urgency. Adding some sort of time limit (even a fake one) would really help...maybe an "earth resistance strength" bar that seems to go down very slowly but is more or less tied to major plot events or something like that.
Also, given how many familiar faces I'm seeing (read: all of them) it's starting to feel like a reunion episode or something.