Pros
Flexible work schedule, education/tech/travel credit available, health spending account, great culture, 32hr work week, great clients, remote work options. Working exclusively with charities and non-profits also means you get to be in marketing without constantly being insulted by a world that hates marketers ;)
Cons
Not a lot of opportunity to work more hours if desired, pay is based on a 32hr work week so can be lower than some agencies overall (though it about evens out hourly). The culture at Frontier is very laid back, informal, and transparent, with quite a bit of autonomy. It might not be a good fit if you're used to heavily structured corporate environments.
(I feel like I should respond to the "staffening" comment in the previous review and mention that is was actually a reference to a point where a large number of people were hired, and not actually in any way a referencing to or mocking individuals who were terminated. I actually only know of two people who were fired in 3-4 years there, so there are a few flaws with that comment.)