Pros
Having been at Wayfair for more than four years, I've seen rapid growth of the business and a few iterations on the organizational structure of the company. Too often, companies are hesitant to make major changes, but those changes have enabled Wayfair to keep up with such significant growth. The company hires many employees directly out of college, and they are given significant responsibility and opportunities as they prove themselves. It's an environment that rewards thoughtful risk-taking and use of data to inform decision-making and business cases. I'd also say that Wayfair is far more transparent than other companies of its size. Employees have access to most financial and operational data through the company's internal reporting system as long as they have the intellectual curiosity to explore it.
Cons
As others have mentioned, compensation, particularly for people that have done very well and are only a year or two out of school, is below market. Generally speaking, those employees will be taken care of as they move into management positions, but there isn't enough separation created between stars and role players at the early levels. The bonus program doesn't create significant incentives - given the limited difference between star performers and people doing just enough not to get fired, there is a major free-rider problem.