The Government Accountability Office just released a report on the USPTO's hiring, retention, and evaluation programs.
http://www.gao.gov/new.items/d05720.pdf
It presents a great external view into the benefits and challenges of being a patent examiner. It is pretty easy to read, with very little "legalese".
I've never worked for the USPTO, but know many people who used their experience as a career springboard right out of school.
Chris Buntel.