Pros
No pros that you can't get at another company. There are some amazing people left here, but not many - most have been layed off or have jumped ship to avoid said layoffs.
Cons
Mimecast is a company that, unfortunately, no longer cares about their employees after being acquired by Permira a few years ago. Rolling, silent layoffs are near constant, so you never know whether or not you're next on the chopping block this month. Benefits have been on a steady decline for years, pay raises and salary are borderline embarassing (and their main NA office is in one the highest cost of living areas in the state FYI), the culture is one of genuine disdain for their workers, the company can't stop hemorrhaging customers due to their lack of innovation. Leadership is chaotic and constantly changing.