I loved it. As someone who is kind of obsessed with the series I found it personally satisfying. I especially liked the way that, by featuring both Shepard and Ashley leading the army into battle, the trailer makes it clear that there are active roles for women in the story - something that was largely missing from marketing for previous games. There is probably a large uncaptured market out there of women who WOULD play more games if they thought there was anything to identify with in them but find most of the games out there to be sadly lacking and/or outright demeaning to women. That was me before I found out that you could create a female protagonist in ME. I am not a typical gamer and am not interested in most new releases, but I pre-ordered the CE of ME3 weeks ago. I may not represent a huge market, but it's an additional market so I think it was smart to feature Ashley (even though I would have LOVED to see Kaidan myself).
I thought it was pretty well done for the audience it was intended to reach, which may be the general viewership of The Walking Dead, including people who are not already familiar with the ME series and wouldn't know anything about the various alien species featured in the games. That said, the story featured in the trailer did not in and of itself show us anything that would differentiate it from numerous other media (games, TV shows, movies) in which aliens come and wreak havoc on Earth, although it was refreshing to see places other than NYC and the Golden Gate Bridge getting destroyed. I actually thought the opening sequence took place in France, which is the only place I have ever seen fields of sunflowers like that.
The quality/nature of the CGI was such that I wondered if there were actors playing Shepard, Ashley, and the husks (maybe with some CG pasted over Shepard's face so he would look like he does in-game). At first I thought that was why Ashley looked odd/different - that they maybe just found some brunette actress to play her. Anyway, technically very well done.
Looking forward to seeing the whole thing on Tuesday.