Vantaggi
The culture of employee ownership and the entrepreneurial mindset that you are allowed to pursue. When I got my start I was pretty young (just out of school) but I was able to get promoted relatively quickly as I demonstrated my capabilities. There are not too many companies where you can find a 26 year old running a multi-million dollar program. The stock based compensation is good as well, but I still don't think it makes up for the lower salaries. The older people who have been there for 30 years don't complain because they have accumulated a lot of stock.
Svantaggi
Compensation isn't what it is at other companies and nothing can drive you crazier than knowing your competition on a bid is another division within the company. Another downside is that its real easy to get lost in the Company, particularly if the work your doing is a niche and not scalable. Its understandable, but they probably lose out on some potential innovation because niche opportunities get swamped by all the systems work. Also, the annual re-organization can drive you absolutely nuts. Its great to have a flexible culture but when you are constantly jockeying for placement, it can get pretty frustrating.