Pros
Joining Wayfair was one of the best opportunities I've ever had. The people are unbelievably smart, leadership is transparent, and I have been able to work on some really cool initiatives and projects. The amount of opportunity, even for someone entry-level, is amazing. New ideas and pushing back are encouraged for all employees regardless of level or tenure. Data is definitely key, though, and it's encouraged to get your hands dirty with analytics. It's also not a place where you can just coast -- the work/life balance is great, but you will work hard and be challenged. It's not perfect by any means, and does have a few flaws, but I really do enjoy working at Wayfair.
Cons
Wayfair is a large company, but it is not a mature company. It does have a lot to work on, process-wise, but it has found a solid identity and has a strong foundation. Wayfair also tends to depend a lot on management consultants as a key talent pool, and while they can oftentimes offer a lot, there's a risk of mid to upper management becoming homogenous, not to mention that there are other places to find strategic, data-driven thinkers.