It starts off with a phone interview asking you the traditional interview questions. After screening you to make sure you're not totally incompetent, they either send you to an on-campus interview session or straight through to HQ.
While their new "state-of-the-art building" is a wow-factor going in, you'll get a sense that something is amiss in the company. The research director was incredibly honest with me in saying they had a very high attrition/turnover rate within the first year. I think he said the number for research associate was 70% if not higher. There is a good reason for that. It seemed like a job you would get bored at very quickly. The pay may be high but the reason they do this is to try and incentivize better workers who won't shirk.
I was almost highly impressed by CoStar until I got through the final round of interviews. I was told I would receive a final decision within the week. I waited a week- no answer. I waited two weeks and placed a call to check in with them and they said they'd call me back which they did not. After finally a little over a month, I call for what was at least the fifth time only to be told that I was qualified for the position but that I was not "passionate enough" about the job and that I didn't give enough details about my experience. Maybe it was because I was recovering from the flu going in. But if you have enough passion for real estate, cold calling and sales, and can convince yourself that you want to stay here for more than a year- then have at it. But don't say the reviews didn't warn you.