Ventajas
Good pay, prestige. The best part of working for ExxonMobil was that other employees trusted that you were an expert in your area and took you at your word. The company generally smart capable people and there are very few incompetents.
Desventajas
Rating and ranking of employees (EADS) was based less on your abilities and more on how good your manager was and whether or not they would go to bat for you as a good employee. Employees are overworked and expected to put in 50+ hours a week. Taking vacation is officially encouraged, but in practice discouraged, except for the last two weeks of the year. US employees have to pick up the slack for international employees. The company is too restrictive in it's practices and is entirely too risk adverse. That means that you will have to fill out a risk assessment for all projects regardless of their value. Expect to carry your blackberry 24/7 and expect to get in trouble if you don't answer an email on a Sunday morning within 10 minutes of getting it.