Vantaggi
The company ordinarily compensates their employees well (including granting a 4 week sabbatical after 5 years of service), and the vast majority of people I worked with were awesome! There are periodic social events (though there are fewer outside of the San Jose, California location), free drinks (soft drinks, coffee, tea, etc.), sponsorship of community events (like World Usability Day), and community involvement is encouraged. There's also a significant degree of diversity in the lower echelons and more than a few career opportunities (if you're in San Jose).
Svantaggi
Work/life balance can get seriously out of whack - there were weeks I worked 80 hours to get a project done and the only reward for going above and beyond was a "thanks" from my direct supervisor. You also have to constantly watch everything you say and do - even the things you think are innocent, like telling people other companies are hiring - there are people who will calmly throw you under the bus if it benefits them (but this is true everywhere). Diversity isn't nearly as pronounced at higher levels and career opportunities outside of San Jose are pretty minimal. Also, there is a significant loss of knowledge capital after people have taken their sabbatical.