Pros
Flexible hours are accepted for most non-production positions. I am trusted to do my work and 'put in the hours" (45+) on average. No body is looking over your shoulder to make sure and this leads to an environment where people feel appreciated and willing to go the extra mile when needed. People of all types work here and I have not seen nor heard of any of the types of racial/other discrimination that a few other reviewers talked about. My guess is that if they are not advancing, they either have a poisonous attitude or are not performing as well as they think they are. One of my favorite parts of working in the technical community here is the copious amounts of learning opportunities, whether it be a Tech Forum class, a cold call to any researcher no matter how senior, or general networking. For one who likes to learn and build/contribute on others' knowledge, there is no better place to work than 3M that I know of.
Cons
If you think that just showing up is 80% of the work, this is not the place for you. Some people may slide by, but don't know how they live with themselves. Bureaucratic red tape is a fact of life in a large entity like 3M. Not fun, but one learns to work effectively within that framework.