Pros
Awesome modern web-based open source ERP product, backed by a great development team and global community. Many different nationalities represented, real international flavor. Very strong product vision and ambitious management team. Lots of opportunity to learn, contribute, and get recognized (even publicly via blogging, forum posts, etc.).
Cons
Still in transition from startup mode to established company, so people coming from larger companies will not necessarily find all of the formal processes in place that they may be used to.