I do this, and occasionally I catch flak for it. I put in 8 hours, and that 8 hours happens to be fantastic -- regardless of how busy I look, what I work on, or who I work with. The problem is that casual observers don't see that. They only see the present.

Thankfully, my efforts were noticed despite my lack of unpaid overtime. I've been promoted twice in the past three years, added to special panels and events, and even been given assignments that just rock.

There is this stigma around working 40 hours a week, and only 40 hours, that I will never understand. If you don't need more 40 (or even less) to do your job, what does it matter? The employer is getting what they asked for, and often times more, and you're getting a paycheck. Its called ROWE: results oriented work environment. Just a shame it hasn't caught on in the US.