Pros
ExxonMobil seems to be a highly ethical company (regardless of what the media tend to report). My experience there was very good, and I felt like the management listened to the needs of the employees. The compensation and benefits package was above average for the industry, and raises were merit-based which provided a great opportunity for new employees to "prove" themselves and be rewarded for it. There was also a general sense of teamwork among most of the people in my department (although I heard that was not the case in all departments).
Cons
The oil and gas industry is still very much an "old boys' club," and ExxonMobil is no exception. Since the company has been around for over 100 years there is a tendency to do things the way they've always been done even if it's out-dated or inefficient. This stifles employees' creativity and makes them robots. Management likes to use a lot of buzzwords and talk about "work-life balance," but it's apparent that asking for a flexible schedule or taking too much maternity leave are still frowned upon (and, as a result, have a negative impact on merit raises and promotion).