Pros
Progressive leadership. Not afraid to fail. Minimal internal politics. Very flat organizational structure. Really care about both their employees and their customers. The delivery side of the business (software development) is exceptional. Well managed recruiting process ensures that they find excellent employees. Impressive focus on continuous improvement. Most of the leadership is remarkably humble. Company is very careful about managing growth -- both in terms of which customers they choose to work with as well as possible acquisitions. Such a strategy has helped maintain quality.
Cons
From an employee perspective, it may be tough to adapt if your previous employer was politically charged. If you have a big ego, DataArt is probably a place where you will not be happy -- it is a "check your ego" at the door kind of place. If you are in a sales or consulting role, you need to be comfortable that while you can increase your income, the organization operates with little hierarchy -- opportunity for promotion is little.