Pros
Pay and benefits are very good, benefits are clearly superior to most of the private sector and pay is right on track. Getting time off is very easy. You don't start off with much leave but you can usually take it whenever you please without respect to others in the office. There is a chance for advancement and the people here are generally helpful when you have questions. The environment is very casual; you can virtually wear whatever you want to work everyday. The building is new, clean, and modern (2006-2007). They are generally trying to bring in younger and more energetic employees; many at the Bureau are older types but there are a significant number of recent college graduates such as myself. You are pretty much guranteed $70,000+ after 3-4 years of working as it seems you get your annual grade increases in most divisions without any hassle. Job security is top notch compared to the private sector. Don't do anything insanely stupid to get fired in your first year and you can easily work here for the rest of your life.
Cons
The Census Bureau is a slow moving place; change takes forever. Even with the top-notch facilities computer technology is very behind. If you are frustrated by high security concerns getting in the way of usability you will dislike the IT division here. It is very difficult to rid branches of incompetent employees so they get moved between branches. Doing anything remotely important often requires multiple clearances from various levels of management, thus slowing down processes. Workload varies - sometimes you are bogged down with work, other times you have nothing to do but surf the Internet. If you are looking for a more active workplace you may have problems adjusting to the style of the Census Bureau; I have many colleagues right out of college like myself and they are full of energy but unable to work to their full potential due to lack of opportunities. Most positions here are competitive after GS-12; advancement can be difficult if you are not well liked by your colleagues and managers, although I suspect this is the case virtually anywhere. The location of headquarters is very bad - Suitland, MD is a ghetto. No matter where you live it will take you a very long time to get to work unless you don't mind living in the ghetto.