Pros
Composite is not afraid to try new things. They regularly innovate, which has made them the unquestioned leader in their space. Plus they put a high priority on hiring very competent people and are not afraid to push out those that don't keep up. I like the fact that they stay very close to their customers and help them when they get into trouble. This happens regularly since the software is used for the biggest and most complex projects by very large corporations. The value that Composite brings to their customers is unquestioned. This is a technical company tackling very difficult problems that others cannot solve. This is a company that takes itself seriously, and takes care of its employees well.
Cons
Composite is really into enterprise software. If you're not, then you won't be happy. Composite is fascinated by the biggest data problems. If you're an application guy, not for you. The work is very technical. Difficult to build and challenging to sell. Not an easy road. The company is not into some of the popular categories like social networking or mobile apps (but it seems to grow substantially every year and appears quite healthy).