If someone gave me the chance of a 30-hour work week, I would rather work 4 days of 7,5 hours than 5 days of 6 hours. Just the hassle of getting up early, dressing up for work, commuting etc. isn't really worth it when I'm only going to work 6 hours anyway. I'd rather take an extra day off.
Being able to work 4 days instead? A god-send. I couldn't think of anything I'd like more. Thankfully, my current job gets me part of the way there -- I work 4 days in the office and one day at home (where I do just as much work but either condensed or spread out during the day depending on the current project workload).