Honestly, I'm a bit disappointed, that piece seems a little bit… chaotic. It starts at a random point and misses some (imho) pretty important ones.
The Rachni, the Krogan, the Quarians, etc. - yes, hopefully there will be some story details depending on how you acted, but honestly, that will most likely be only minor plot elements. The romance option? Important on a personal level, but for the overall plot it's next to meaningless. The base? A big question, fair enough, but not really THE big question.
Honestly, the imho most important question hasn't been mentioned: What are the reapers? Where do the come from (meaning "Who created them?")? Why do they do what they do (harvesting civilizations)?
And this is the big question, concerning ME3's story. Of course, there are other things that make a game nice, but the reason why I will buy Mass Effect 3, no matter if it's a shooter or an rpg, is, that I want to see a nice and creative answer to this question. The answer can either be a good one, creative, perhaps even surpising, but still logical or it will be a bad one, meaning either boring or illogical.
