While I think that a shorter work week is an good idea, I don't see it happening. Right now I'm working for a university research lab and worked a 20-hour week over the summer. I hated it. I couldn't get anything done in 4 hours a day, and over the course of a week I didn't feel like I had really worked as much as I should have. And then, after getting off I'd just dick around for the rest of the day. That doesn't mean that I don't find 40-hours a week to be oppressive, I'd love to take a longer break from work every once in a while, but I don't think a shorter work week is the answer. Rather, I'd like to see at least a month's worth of vacation days, and a flexible work schedule. Some days I really want to get in to the office and work for 10 hours, but other days (like Fridays) I really only want to work until 3 or 4, after that I'd be totally unproductive. Its still 40 hours a week, but its the 40 hours that I really feel like working, NOT the 40 hours that the work week mandates.
I also work in research, but I think the experience you describe applies to many areas of work. Flexibility and working when you are able, and not being forced to work when unlikely to do so or it is impossible accomplish anything meaningful. Being required to fit your work into pre-measured buckets isn't practical in many cases, sometimes the buckets would be overflowing and other times they won't be filled up all the way. The problem often seems to be the slightly empty buckets and not all the potential work being lost as overflow from the full ones. Hopefully that makes sense. The trouble is, this requires accountability and trust in employees that managers and HR departments find difficult. Being able to take time off and not be forced to work rigid hours seems to be a better approach than simply working less. Ideally people should be hungry for work, they need to be enabled to do so in a fulfilling way.