Pros
Probably compensation is good, but if you are laid off before getting the shares, you basically worked for free.
Cons
Old technology. Full of duplicated internal tools doing a bad copy of what open source software does 100X better. Ugly and uncomfortable offices with not even enough restrooms or places to eat, visible pipes (except if you are on HR floors, which are another world). Most overrated colleagues, once you get to a certain level, you become a demigod that can do or tell pure BS, but your opinion is always the one that would matter, no matter how wrong it is. Full of disloyal people that won't hesitate to betray you to cover their own incompetence. Huge lack of technical knowledge or the chance to work with smart people from whom you can learn new things. Completely full of the "project management" BS, meaning many hours spent each day on useless meetings, endless scrum/agile/BS processes, more focused on counting story points and all that BS that in really developing quality software.