You are constantly faced with new things to learn, if you love learning/being challenged then you will fit right in.
Benefits are great especially compared to other places I have worked in the past.
Cons
As with any fast growing company there are growing pains.
Everything is super fast paced and it can be hard to keep up.
I have yet to find an actual con. The closest I can get is "Startup Growing Pains" but that's to be expected and I think they handle it better than most.