Pros
It's a very large company with lots of room for career advancement. Since the company is so large, there's also the opportunity to change careers later if I chose to switch careers. Compensation seems to fair when I look at what my friends at other large companies are making. However, this may not be across the board. I originally applied for a different position at Compass where the starting salary was way under market for the position. Needless to say, I did not take that position until something better came along. Pay increases also seem to be slightly above average, up to 5.5 percent or so. Also depending on your position, there may be occasional market study increases. These are usually on in very specialized positions.
Cons
Sometimes the company seems too large. With about 360,000 employees, it's harder for your work to really stand out. You have to be that much better than your co-workers when it comes to promotions, especially in a large department or area. The impact of your work to the company can seem to gets lost with so many sub companies, departments, & areas. I've worked for other smaller companies before, & it's definitely better to have fewer bosses or "higher-ups" over you. It just means that there are that many more people to try to impress & people's toes not to step on.