Pros
Very comfortable place to be, great benefits, for many employees a 35 hour work week. The turnover is low and people are generally very happy here. The benefits are great, with 75% tuition reimbursement, lax leave policies, 5% 401k match, and bonuses. We also have a pension that you will be vested in after 5 years of service, which is a pretty rare thing these days. The work you do here is generally very appreciated. Also, the work can be pretty exciting, depending on what you do. Its interesting to be involved in a number of the facets of energy policy.
Cons
The different functions of the organization make for a disjointed cluster of departments and specialities. This makes advancement and career development somewhat awkward. This is a good place to end your career or a place to work while API pays for school, not a place for growth. Some department are an absolute dead-end. Also, some people may have a political/moral issue with working at API. As a conservative-leaning person, I've always drank the cool-aid and have felt a certain satisfaction in working for the industry. More liberal leaning people may have more of an issue with that. Either way, get ready for political arguments with friends and family.