Ironically, a lot of the complaints as to the introduction being rushed are derived from it having little to no association with the last DLC, which was supposed to be a lead in to this game. Essentially Arrival ends with Shepard expected to go to Earth and stand trial. ME3 starts with the trial having come and gone. I don't think the demo even references it at all.
Agreed. Bioware seems to have a problem with missed opportunities in ME. First, they kill Shepard in the beginning of ME2, only to bring him back in the next scene and then never substantively bring it up for the rest of the game besides the passing "I thought you were dead" (IMO Shepards death takes so much of the tension out of rest of the game and only stands as a way to jump the timeline forward). Then they build up Arrival, warts and all, then skip the trial, have Shepard relieved of duty, only to have him gain it back in the next ten minutes. Why do it at all? The player doesn't gain ANY insight from having Shepard be a civilian and are already back to the normal state after the intro sequence. I would have loved to see a more deliberate intro (your suggestion is great EatChildren) and then have the Reapers attack so the player could actually build some investment in Earth and the characters instead of going for the AAA "start with a bang" intro.