I thought the biggest factor for me in work happiness is the people I work with. I realized that's important, but they reason I'm so happy now is the amount of control I have over my own time. As a telecommuter, I work when I want to work. It doesn't have to be between 8 and 5. As long as I get my stuff done on time in a high quality manner, my boss is cool.
I have to wonder if control is a bigger issue with Gen Xers than with other generations. We've struggled with controlling, process-oriented Babyboomers for many years. For Boomers there is one right way, one solution, one track. For Xers, there is one right result, but many roads to get there.
I know when I say Boomers are controlling, it may upset some of my Boomer readers, because they don't think they're controlling. However, there are many many of us Xers who have been slapped in the hand because although the result was correct, we did not do it the "right way." We've been dressed down for not following the appropriate "steps." I'm not a "down with Boomers" gal - but this issue is something both our generations have struggled with.
I still invite you to take my poll. If control is your happiness factor, go ahead and post it in comments.