Nice people, respectful of each other, definitely some rapid growth challenges, but in return lots of opportunity for professional growth, fun challenges and fast paced, so no monotony. Not for a true 9-5 person, but there is a good work/life balance if you allow for it, and have good time management skills. You can easily find yourself working several hours overtime, but 80% of the time its how you approach things.
Overall a good place to work, and the challenges are no different than what you would expect in a fast growing company. Business side tends to set expectations for project deliverables that do not always make sense or are feasible for the technology group to deliver on.