Pros
High paced environment with great scope for learning, and extremely energetic, ambitious yet humble team. Importantly, I feel supported when needed by my teammates and management. I know I can feedback issues, and I feel I have much leeway to express what goes well or not well. Overall, Tier has great opportunities ahead.
Cons
A job at Tier requires a high level of autonomy to set your priorities and adjust your scope as you see fit. This is the nature of any startup job I think, but could be unsettling for those coming from different environments. The pace is intense. There is definitely support from colleagues and management alike; It feels like it's down to the individuals to set their own limits though. Be careful not to be drown under too many projects.