Pros
Sherwin-Williams is a big company with a lot of opportunity, strong growth and stability. They've been around since the industrial age and will be for quite a while as long as they keep their heads in the game. I was a co-op student there and I learned a great deal from my mentor and co-workers. They were very flexible and understanding in terms of my school schedule. This was in the heart of the recession and they saw fit to keep the research groups going strong so they would come out of it even stronger. I got to work with a wide range of innovative products and even travel a bit. I have since moved on of my own accord but I would go back if a suitable opportunity presented itself.
Cons
Typical office politics, so watch yourself in the same way you would anywhere else. Big Company corporate culture can be difficult to grapple with. The company is often driven by marketing (at least my group was) leaving employees to contend with a few ill-conceived products and projects. The words "what in the world are they thinking" came to mind a few times when dealing with marketing. I left because my particular field was mechanical and not chemical, leaving me little room to move up at the time (they have since improved, so I hear). Chemists and Chemical Engineers can go far here, so can the folks with business degrees.