Pros
This was one of my favorite jobs! Great comp and benefits plan. They take really good care of their employees and go above and beyond to make sure you have the resources you need to succeed, especially in the sales dep't. Very little red tape (i.e. expense reports) and a trust that you will "run your business" with integrity. They put a lot of effort into hiring smart people with very diverse backgrounds, which I think is the key to MongoDB success. I was always learning in my sales role, constantly improving both my technical acumen and sales approach. Awesome sales & marketing lead gen teams that are constantly running campaigns to help fill your pipeline. Great benefits, unlimited vacation time, no 401k match. You will get fat from all the free food they supply you with.
Cons
Typical fast growth, tech startup concerns-- Constant change, inconsistent messaging. High turnover rate due to changing needs of sales org (letting unnecessary managers go) and due to very high expectations from individual contributors. Very intense monthly/quarterly business reviews with sales management and VP's (not for everyone). Be prepared because they WILL grill you on EVERY opportunity in your pipeline.