Rian Johnson is the director of Looper, and he took to Twitter to warn you: if you've already decided to see his movie, you should maybe skip the trailers. It's not that there's anything particularly spoilery in them, it's just that he thinks you'll have a better time if you don't watch them. That only applies if you're making plans to buy tickets - everybody else should watch this trailer.
I have seen Looper (or a cut of Looper; I hear things have changed since I saw it and wrote about it here) and I think it's excellent. I also think the new trailer doesn't give too much away - it is more or less giving you a sense of the larger scope of the story, and what Bruce Willis is trying to accomplish in the past.
The trailer also gives you more of Joseph Gordon-Levitt's take on a young Bruce; what I like is that JGL isn't imitating, he's embodying. It's a truly great performance that proves Levitt is more than a pretty boy - he's a real actor willing to be submerged in a role.