It was pretty good, though I think the incredible popularity may have inflated my expectations, so while I enjoyed it, I also expected much more. Oh, I should mention the only spoilers I know are that Vader is Luke's father (Anakin?) and that Leia is his sister, otherwise I'm completely blind.
Anyway, my biggest issue is the pacing, it gives no time for the characters to react to the events of the story, or for the viewer to take in the more tragic scenes.
For example: Luke sees the burnt corpses of his on family but he is immediately ready to go on an adventure to avenge them; Alderaan is destroyed but after the initial shock, Leia is ready to fight for the revolution; Obi-Wan "dies" (he obviously survived) and Luke has a very quick talk with Leia but that's it. There's no breathing room, the movie seems like it is in a rush. I initially thought their acting was the reason, but since I found the main trio very charismatic and loved the androids, I find it hard to put the blame on them.
The story itself had some really dumb moments, like R2D2 being able to hack into the best military base ever (isn't he supposed to be a really common model of android?) or the fact that the Death Star has an opening that goes directly into it's core (really? how do you overlook that during construction? that's just idiotic).
I also don't really like the Force because it seems to be just a very convenient excuse to have things happen, specially during the final mission when it allows Luke to hit the target. Luke even mentioned before how it was just like throwing something in the rat burrows in his home planet, I was sure we would see a connection there to justify him saving the day! I would've preferred that over the Force helping him.
Also, Vader! What a surprise! I imagined he would be much more threatening and... distant from regular people. Right now he seems like just a particularly powerful soldier of the empire, he isn't even the highest raking member apparently? Damn, my view of him was completely different, I wonder if his role in the other movies will help me see why he's such an iconic villain.
Overall I liked it, a very entertaining movie from start to finish. I hope the main cast stays the same, and I'm very interested to see if the other movies will show me why Star Wars has such a massive following.