Pros
Learn a lot, have the name of a big company on your resume.
Cons
Can't speak for the organization as a whole but I was in the consumer and office business and it consisted of a few unhappy individuals who were trying to outshine one another. Very political and as a result it facilitated a lot of gossip and a "happy" group of lower level staff because of certain common enemies. Co-workers on an individual and personal level are mostly super nice and sweet. It's only further up the food chain within the dpmt that claws start to show. Contributing factor is favoritism, though the manager is extremely defensive about this and denies it through and through. Finally, though it's 3M, it's managed very much like a local company with an inordinate amount of respect to the international counterparts, for no justifiable reason.