Pros
MongoDB is an outstanding database product as proved by the many customers who have used it. It's fast, flexible, and it delivers the business value it promises -- Can't beat that! The culture is a classic start-up with a long way to go to profitability. It's kinda shocking that the investment bankers have convinced the market that a company losing money for multiple years is worth $1.6B.
Kontras
Just like every software product it has problems. But the biggest problem is its commercial model. Buying the product may serve well the small organization that's going to spend $70K so they get "Enterprise Support", etc. But the large organization that would otherwise spend $millions can just download the free version and hire a technology team to support and promote the product internally. Prospects say to our Enterprise Sales people, "Why would I pay for that when I can download it for free and support it myself?". MongoDB blames that on Sales. Now, that's an easy "cop out". Maybe MongoDB needs to revise its commercial model and stop bleeding money and going to the market for more capital, since the firms revenue can't seem to pay its bills.