Pros
Amgen is a place that is hard to leave. The people are generally nice (if you don't work in Thousand Oaks) and the benefits are the absolute best. Everyone gets 5 weeks of vacation plus a good health plan. Most people are only working 40 hours a week and everyone gets a year-end bonus unless you are really screwing up.
Cons
The biggest downside is lack of career advancement. If I stay at Amgen for another 5 years, I will likely be in the same position for all 5 years. The only opportunity I will get for a promotion is if my boss leaves or is promoted. Of course then I will be competing with everyone else in my group for that one spot. If you don't get it, keep waiting. It doesn't matter how well I perform as there are very few manager positions and those managers have a sweet deal so why would they leave. This is probably more true for people working outside of TO but it still sucks just the same. If the benefits weren't so good, I would have left. But it's hard to leave a really comfortable dead-end job paying reasonably well with 5 weeks vacation and only needing 40 work hours a week.