Pros
EPA has an important mission and there are many exciting things going on in the environmental field right now, like climate change and green jobs. EPA has many competent staff level people who really care about the work they do. EPA has flexiplace (work at home) program and flex hours. EPA has a transit subsidy program. Good benefits, generally, altho dental benefits are not very good. Lots of opportunities to move around within the agency and get different experiences. Generally, very flexible on leave for personal reasons such as caring for a sick family member, and they have a leave bank program.
Cons
Right now at EPA there is a lack of management support of scientists within EPA. If you want to know more about this go to the Union of Concerned Scientists website and read the report they did on this topic. Sometimes it is difficult to make things happen within such a large agency where there is so much paperwork to make anything happen. In this administration, EPA is underfunded. There is a lack of sufficient funds for training, travel, awards, etc. It's really hard to do your job well when you are based in SF, but supposed to cover Nevada, Hawaii, AZ, CA and there's very little travel dollars.