Pros
Great culture. Lots of smart and friendly people. Solid benefits including on-site extras. Many difficult, challenging problems to work on. Lots of opportunity to grow and be part of something special with financial upside. I read all of the Glassdoor reviews and Quora comments before joining earlier this year. You need to take them with a large grain of salt as they are limited, older data points. It's a great place if you like to work hard and enjoy delivering results that make a difference.
Kontras
Everybody has accepted a less than market compensation to be here. Although, Square does try to make it up with options as do many startups. Minor point - no 401k match is a bummer for savers, but again understandable given the close management of cash.