Well I'm sure they can look at the dailies if they wish, but yeah, they have no idea what the film is going to look like edited together. Or with something that is FX-heavy.When the actors are filming the scenes, they have no way knowing what the finished product will look like, so it has to be very exciting for them to see it for the first time.
That's right - which is why I said "finished product." I wonder how silly they must feel when they are dancing around in front of a green screen with little tracking balls glued to their costume.

I've seen some complaints that the tone of the trailer is too serious. Too reverent. I think that's a great thing. For one, I think it shows a perfect idea of fandom. We do look at the OT as our legends, sometimes perhaps a little too reverently. Plus, if the idea is that our knowledge of OT has fallen into myth, and these people want to be free and want more, then why wouldn't the characters show such reverence as well?
You know what people? Star Wars is a masterpiece. It deserves a little reverence. People should take off their shoes when they watch it because they are standing on Holy Ground.