Pros
Creative, empowering, fast paced environment where you can learn a lot very quickly. While some see this as a negative, I personally love the fact that things move quickly, and are constantly changing. MediaMath allows employees to be themselves, share and implement new ideas, and get involved in really cool projects. If you are hardworking, have a great get-it-done attitude, you can be very successful here. If you are entitled, lazy, or negative, you probably won't last long. It's a very adapt or move out culture where the top performers are rewarded and those who can't handle it move on. Great benefits and perks - beautiful offices, snacks and drinks, fun events like Trivia night and flip cup tournament, open PTO. You get treated like an adult regardless of your role. Work hard and play hard.
Cons
Yes there are constant changes to the org - but it happens in every company! Management has done a much better job of providing more info to teams about company vision. Some managers aren't flexible about start and end times which seems a little draconian, but most teams are pretty flexible.