Time at my job: An official 8 hours of butt-in-chair. Actual work: usually more like 4 hours. (This is on days without meetings! The things I'm doing right now have a major bottleneck caused by a programmer fresh out of school who did not realize the dire consequences of generating 4000+ subdirectories automatically and checking them into SVN. I don't mind; I probably would have to find other ways to spread out my work time if it weren't for that.)

Time doing "my" work: 1-2 hours on weekdays, 4-6 hours on weekends. The stuff I'm doing is 100x as interesting of course, and I don't have to communicate, so I'm probably 10x as productive. I find that by the end of the weekend I'm always a little shocked at having to come into the workplace and slow down again.

For a few months recently, I found it really, really hard to get things together at the end of the day. Then I realized that a significant part of the problem was because of blood pressure; it's higher in the evening, making it harder to concentrate, and I had let my average drift upwards as well by eating junky stuff.

Now I try very hard to get it down - diet during the day, 20 minutes cardio after work - so that I can stay productive in the evening.