Pros
People - The crowd here is a bunch of young, bright and enthusiastic people and it was a pleasure to work with them. Most people end up as very good friends even outside of work. Meritocracy - Promotions here are based on meritocracy and there is very little politics. Launching a software career - If you're interested in a long term career in software, this is a great place to rapidly pick up the skills needed.
Cons
Lack of structure - Being a small company, there is often a lack of structure in the way work is approached. Often there is not enough top-down communication, ad-hoc solutions are implemented and the emphasis is only on getting the job done. Hours - Perhaps as a consequence of the lack of structure, there are often times when teams (both on the tech and consulting side), need to put in long hours. Mentorship/career advisors - Very little of this going on. I do understand that Appian has consciously been making efforts to address some of their weaknesses though so I expect an improved company in the future!