I think most of my disappointment stems from expectations. When I heard "trailer" I actually thought something more akin to a bunch of various clips illustrating different parts and aspects of the game with some epic music and quotes framing it. This was pretty much just a chunk of cinematics and gameplay illustrating over-the-top action related to only one place and mission. Not really what I'd deem a "trailer" my any means... it's more a slice of a specific piece of the product ripped out and shown, albeit likely sped-up with some bits cut here and there. Simply put: it's really no more a trailer than watching those clips of Anderson and Shepard on Earth and the Sur'kesh demos are trailers.
That said, it has both it's good and, well... not really "bad" moments per se, but perhaps overdone moments. I mean, to get one niggle out the way, how many times are these action moments going to begin with Reapers stomping around and beaming things resulting in Shepard being shaken up and/or crumbling debris sending him rolling down something before resuming gameplay? It was impressive and neat when I first saw it in the Anderson/Earth demo with that shockwave sending them sliding down, but after a similar occurrence in the Legion/On-the-rails demo and now in this so-called trailer, I can it's going to get old fast if it occurs much more in the game. Seems everywhere Shepard goes he/she can expect an earthquake and some tumbling.
My other main beef is basically, "Oh yay... more action, TPS style gameplay. Just what I want to see more of!" </sarcasm> <_<. To be expected to a degree I know, but perhaps this relates to my first point: an actual trailer that illustrated various aspects of the game and not just combat, explosions and Reapers shaking Shepard up would have been more appealing. It's easier to swallow in smaller doses and when peppered with a few other aspects besides "Action! Action! Action!"
That said, the cinematics and transitions are good and well-directed. I did love the initial image of the fighters zooming overhead and the Maw vs. the Reaper was well done. Not too much shaky-cam or 2 second shots, and everything was nice and focused. Good to see the overall style of cinematic direction remains consistent/classic and it hasn't been taken too over-the-top and modernized. I'm still not a fan of these mini-crab tank Reapers because they seem to be the same thing I've seen before in dozens of games lately, but I guess there's not much I can do about that and I'll just have to put up with them. The section of gameplay itself looks kind of interesting (i.e. with Shepard advancing and trying to avoid the deadly red beams and Reaper feet), but I'd have to actually feel how it plays and experience it directly to really judge it. I can see from the style it could either be really fun, or fall victim to being annoying, depending on execution. It'll depend on how random or scripted the section is, and how punishing it can be or not. Too on-the-rails and predictable and it doesn't feel dynamic, but too random and punishing and it becomes frustrating. It'll be interesting to see how it balances.
So, overall, a tad disappointing, but nothing that really makes me roll my eyes or rage. Again, largely due to expectations I admit, but while it impressed me somewhat with some neat moments, it didn't outright "Wow!" me overall. Perhaps if the Reaper vs. Maw thing hadn't been spoiled right at the start of ME3's advertising in the Gameinformer article it would have been a different story. That said, at least when they show this, I'm not being spoiled with anything massively awesome prior to playing I had no prior knowledge to. It's both a blessing and curse in that regard, but overall I think I'd rather be surprised and "wowed!" in the game itself rather than by a trailer (sorry... "trailer").