Okay, here are some of my initial thoughts:
1. Bad Timing. Star Wars just released an AMAZING teaser a day earlier. This teaser, while not bad, suffers in comparison.
2. Visual Design. It is difficult to tell from just this tease, but it seams like director Zack Snyder is abandoning the more realistic photography of Man of Steel, with its location shooting and direct lighting and going for more of a CGI feel ala 300 and Watchmen. This isn't necessarily a bad thing, but I really liked the tactile feel of Man of Steel.
3. Affleck. I'm digging Ben Affleck as Batman. In the regular suit he looks like he stepped right out of the comic book. I also like the fact that they didn't make him try and do "Batman Voice," but filtered it electronically.
4. Themes. One of the things I like about the teaser is that it seems to deal with big themes of hero worship, even when the hero doesn't want it. I remember watching Superman IV: the Quest for Peace and watching the entire world give over its power to Superman like it was nothing. This movie seems to be addressing a more real-world reaction.
Overall, this was the tiniest of teases. The first Force Awakens teaser was fine, but it didn't blow me away. That's how I feel about this teaser.