Pros
New things to learn and work on every day; the company's product is always evolving; you aren't stuck at your desk (unless you want to be); the people are friendly and welcoming; plenty of upwards mobility (company tries to hire from within rather than external sources); thorough job training; opportunities to travel; HR promoted events, activities, and discounts; free coffee; your department becomes your second family; great benefits; product discounts that you will definitely use.
Cons
Can be pretty stressful at times especially around new product launches; interdepartmental tension; a select few people who like to cause scenes; every department has at least one freeloader who dumps on the work horse; the company tends to lack concern at times for product quality; job openings tend to be offered to lower level employees first which results in larger turnovers and positions that are filled by employees who wouldn't necessarily be best qualified; company as a whole resents change as a result work toward positive change is slow; finally the company is growing so fast we are running out of room (parking issues, product storage issues, open cubes are dwindling... wait should this also be a pro?)