When i first graduated law school I wanted to work for a federal agency as an attorney - 6 figures, go home at 4, no weekend work, 3 weeks vacation, great benefits.....too bad everyone else wanted that too since the working conditions in the private sector are tough as a lawyer....and that was while the economy was booming....I can only imagine how difficult it is now. But yes, I'd work for the feds in a heartbeat.
I know a few attorneys who work for federal agencies. None of them are out of the office before 6:00 p.m. That being said, I'm sure their hours are still better than what you would find in the private sector.
Most government workers in professional positions work pretty hard and, as has been mentioned, some private sector companies offer comparable benefits to government jobs. The big trade off, as I see it, is stability versus salary. Many of my friends out of school made more money than I did, but today I'm the only one who is 100% sure that I'll still be employed 6 or 12 months from now. With the economy in the toilet and a new baby, I'm happy to not be worrying about my job.