The Bothan spies got the plans for the second Death Star, not the first one.
I agree with Serenity, this is the best Star Wars movie made to date. And by a significant margin in my opinion. There was nothing I didn't like in it and everything was executed skillfully. The only thing I found lacking at times was the music, but it is still an amazing achievement from Michael Giacchino who had only four weeks to score the whole film after Alexandre Desplat walked out.