As a fan of Star Wars (Have to admit, though, I've never read anything from the Extended Universe, so, mainly a fan of the main films) I found the trailer and movie concept quite interesting.
It's a breath of fresh air that the next Star Wars movie will focus on the Rebel pilots instead of mainly on the Jedis/Siths, so I'm definitely going to watch it.
Personally, though, I'm not always too fond of prequels because, unless they show the impact those previous events had on future installments, as well as the return of, at least, some of the new characters introduced in those previous events, then I think that their reason to exist is simply just to make another installment of a certain franchise just to win more money knowing that fans will watch it.
Again, that's just my opinion, and not all prequels are bad (Not talking about the Star Wars prequels, although, episode 3 was really good), in fact, some have proved to be vital for a series (Since this is a gaming forum, think Metal Gear Solid 3 as an example).