I'll make this a more reserved reply than I made my earlier thread (which got closed due to overeager moderation).
There are a few things in this demo that absolutely did not work for me. Most notably the section on Earth for a series of reasons:
1) Conversation is wooden. I didn't understand why the Council was asking Shepard what to do. The answer Shepard gave were uninspired one-liners that resolved nothing. Why is the council in despair when it should be ordering a planet into defense? Why does that guy ask Shepard what they should do, when the answer "fight" is so obvious it does not even deserve to be asked? Why is there no real leadup? I didn't feel any urgency in this section.
2) Everything moved from setpiece to setpiece, which made it a stale affair. I am not saying this to be bothersome. I'm saying this because I feared for poor writing in ME3 after what happened to DA2, and this demo has confirmed some of my fears. First there is the "oh my god the reapers are here" part with the council, but since its not the citadel council the players are robbed of any chance to feel vindicated for their treatment in ME1 and 2. We don't know who these councilmen are, why we should care about their fear, or why they're so horribly inept. We don't even know what they're going to be doing. Wasn't this supposed to be a trial? If not, then what was the purpose of this? The hallways walls still read Courtroom Access, so as a player I have no clue whether I was talking to judges or councilmen or anyone.
Then comes the part where the Reapers land. They start destroying a nondescript city that we are given no description of. Where is it? I'm serious, I have no connection to this city. All I see are sterile white buildings being destroyed by giant alien robots. Any chance for the player to feel awed or saddened is lost, because we never get pulled into the action. It's a background setpiece that does not involve the player, and we are not given sufficient reason to care. The trailer was good because we saw the Big Ben and the Eye of London. The beginning of ME3 is bad because prefab skyscrapers in a generic future city without a name incite no feelings.
The same is true for the bit with the child later on. Who is this child? An opportunity is wasted when Shepard first sees him playing with his airplane to give the kid a family. Why doesn't he have one? Why is this one lone kid running around without any supervision? Why doesn't he have a name? Who cares about "Child". Why not call him Eric, and why not have Eric at least play in that little garden under the supervision of his mother? And then why not add that mother to the bit where Eric dies, leaving her standing amidst the rubble? Who cares about Child. Child is as alien to me as the city he lives in. Any attempts at evoking sympathy from the audience fall flat, because the audience is not fooled into believe that this is a human being. For all we know, he's an extremely advanced japanese robot. I don't know.
Then there's the part where the Reaper shows up and destroys the refugee pods. Why not the Normandy? This Reaper must be the dumbest Reaper ever, because it does not act on the information that must surely be in the collective Reaper database about the Normandy and how often it has thwarted Reaper plans. Instead, it kills Child the Japanese Robot.
In the meanwhile Shepard watches the war evolve like she's a spectator in a theatre. Refugee transports get blown up RIGHT NEXT to the Normandy, but Shepard just looks pained, shrugs and walks in. Really? No urgency? No commanding Joker to make it fast? Instead, Shepard spends forever in some strained dialog with Anderson that really couldn't have been held at a more ridiculous location. Why there? Why not earlier? Why did Anderson not communicate during the earlier bit in the building where they climbed past a chasm? Instead he went on about "oh my god people are dying." You know that there's a classic adiago in writing: show it, don't tell it. If thousands of people are dying, I need some proof. Anderson talking about it in a setpiece building demonstrates as little to me as Anon Kid dying or as this sterile looking city getting destroyed. I have seen not one person die when Anderson says this, despite his claims.
The demo gets better in the later section with the Krogan Female, because you get into typical ME gameplay which redeems the game. But I am under no illusion that the writing throughout ME3 is going to be any better than what the opening tutorial sequence has shown us. It turned out exactly as I feared.