Pros
I have been with Synack for a little over a month now and have truly enjoyed coming into work everyday. The people I work with are the best at what they do, are extremely motivated, and insanely intelligent. At the same time, though, they all know how to let loose and have a good time (especially during our weekly happy hours over some ping pong, foosball, and board games). We also have a very open working space which helps foster collaboration between various teams and everyone is extremely approachable and willing to lend a helping hand or explain a complex concept until you fully understand what's going on, including management and leadership. Some of the extra perks like catered meals, a stocked snack bar, and an onsite gym with basketball court and swimming pool are just the cherries on top of it all.
Cons
Thus far, the only downside of working at Synack for me has been the commute, but with the flexibility and understanding nature of our leadership, and my manager in particular, it hasn't even been an issue.