Pros
Lots of smart and nice people. Employees believe in the product, and genuinely want to build stuff that helps people. Stable and profitable company, isn't going to disappear any time soon. Pay and benefits are great. Wide variety of snacks. There is such a thing as a free lunch, and a nice one at that. Friday breakfast is fantastic. Many people have lunch together at a communal table which is a good way to get to know each other. Free valet parking in the building.
Cons
Tech stack is custom and ancient, source code is a mess, mountains of technical debt. On the positive side they are aware of these issues. Because it's a small company with only one product, there's a limit on how much you can grow & change in your career. Lots of interaction over slack, even if the person is 10 feet away from you. Sometimes that's best, but overall I'm not a fan of that. Too many snacks = more time at the gym.