Pros
I reference Malcolm Gladwell's book Outliers in the title because if you are able to move up the ranks at CoStar, it is because you are the exception to the rule. I basically lucked out and have been able to be promoted every year or so into a more interesting role, and I started off as a research associate. The benefits package is excellent, the company is in no risk crashing and burning and there are many wonderful people who work here.
Cons
That said, favoritism is rampant. Upper management is particularly out of touch with the research department. Scare tactics and a sink or swim atmosphere dominate the culture of the workplace. The majority of employees are unhappy and management doesn't seem particularly interested in why. There are shady individuals at the top who are casting a shadow on the integrity and ethics of the company.