Pros
The people that work for GM are generally capable, respectful, and congenial. It is a great place to work if you are looking for a nice and welcoming work environment. People are always willing to help one another on projects or with questions. The managers also genuinely care about their employees and want them to be happy and successful as much as possible. There is also a great technical education program for those who are interested. It is possible to complete advanced degrees and improve one's skills conveniently and at very little cost. Finally, the working hours can be very flexible for those who have special circumstances or when unexpected events arise.
Cons
In general, GM is not a well run company with many obvious areas for improvement that senior management seemingly chooses to ignore. Additionally, there are very few opportunities for advancement even for talented employees. The reason for this is that as the company has gotten smaller it has also gotten very top heavy. There are a large number of managers and senior executives with seemingly little responsibility. Many of these managers have few employees that they supervise and their responsibilities are only slightly greater than those of the employees they supervise. As a result, it is difficult for younger employees to be promoted to leadership positions because there are already too many managers and not enough employees.