I love this movie. Throwing that out there first. Second, it's not a perfect opening but it multi-taskes. You get character, story, and foreshadowing. No question there's a ton of exposition. Regardless I think it moves the story in a way doesn't bog down the movie.

One thing this opening does is do a little dance between exposition and surprise. As the camera tracks along, there's some clocks, then the newspaper articles on the wall, then the coffee machine coming on, then the TV news item, then the burnt toast, and so on. It's a way of doling out the information sandwiched between fun bits of business.

I recall reading an early draft of this flick during the 40 Day Script Challenge a while back, and it's opening was completely different - started with Marty in a classroom, atomic bomb plumes reflected in his mirrored glasses as the class watch a educational film on plutonium (I think - it's been ages since I read it). However, most people have mentioned that this scene is chock full of exposition, but I feel it's done well - probably because we, as viewers, are completely fascinated at the sight so many clocks at once!