Pros
General Mills is a great company to work for, their entry-level positions are in-line with other organizations if not higher, and they provide great experience in the consumer-packaged goods field. They provide the leadership, mentoring, and support team that can deliver a higher percentage of success with their hires. The hierarchy of promotion lends people to feel good about being promoted, as the ascension up the chain is easily visible. Also, the strong affinity groups lead to great acceptance of diversity, which is something not seen in many companies. They make you feel important, and your voice is heard by everyone.
Cons
Some of the downsides of working for General Mills is the "GMI Way" as in you do it the GMI Way or hit the highway. I believe that for someone who comes into the company as an "experienced-hire" candidate might not grasp onto the norms and the learning curve that is associated with the job and the culture of the company. If you come in as an experienced-hire and do not fit in originally then your options become severely limited. Also, with their headquarters being in Minneapolis, it isn't the greatest destination for someone trying to ascend the corporate ladder.