Pros
3M is a large company, there are many opportunities (depending on your job function) to move around the company. Benefits and pay are good. Amenities at 3M Center (HQ) are great (fitness center, cafeteria, hair salon, pharmacy).
Cons
The company is stuck in it's ways. Unbelievably behind the times. Things are done 'the way 3M has always done them' You waste more time in your day doing everything the hard way (manually) because there are no computer systems robust enough to compete at the level the company tries to compete at. There is an extremely large percentage of people who have been at the company forever and have a 'politics clique' against anyone who challenges their methods or ways of thinking. Management is quick to defend/cover up the errors of long time employees.