Pros
CoStar provides all of the trappings of a publicly traded corporation, including above-market compensation, benefits, amenities, facilities and corporate perks. There are lots of kind, talented and competent people who work at CoStar, and if you're lucky, you will land on a team full of those people.
Cons
While good work is typically acknowledged and rewarded by your immediate manager, the ultimate decision-making all happens from 30,000 feet by a mercurial billionaire founder/CEO, and these decisions are in informed by the performance of the share price rather than the performance of the people. This means that your job security is often dictated by forces that are entirely out of your control, making individuals feel like chess pieces and the company culture feel like the Hunger Games. Individual production numbers are projected onto 65-inch screens on every floor while HR leads new hires on building tours saying, "don't worry about the numbers, nobody looks at them and the trackers aren't even accurate." Entire teams are erased without warning, only to be rebuilt again 6 months later. Middle managers are regularly shuffled around to lead teams outside their areas of expertise. Based on my experience, most people work at CoStar no longer than 18-24 months, half of them leaving voluntarily and the other half being unexpectedly laid off. Those 18-24 months can be valuable for your professional development and financial well-being, but do not expect to build a career at this company.