Two years ago I switched to 30 hour week, and there is no way I'm going back. I'm happier, in better shape and get so much more done at home.
I do understand why people work like crazy, they have huge mortgages or other loans. I cut my hours before taking huge loan (I have smallish student loan to pay), so I just need to adjust my future house/apartment to my income. It's much more easier this way, than to first take huge loan and the trying to cut hours.
But for my friends who don't have that much debt, I always recommend them to work less. Here in Finland we have quite heavy progression in income tax. It makes the pay cut smaller, since your tax percentage goes down. And if you have small kids, kindergartner bills goes also down, since you can pick them up earlier.
It's amazing how big difference two hours a day can make. Nowadays I exercise at least three times a week (I lost 10 kilos this fall, yay!), I cook better and healthier food and do some programming as a hobby.
Before cutting my hours, I made more or less average pay, now my salary is pretty much the same as median salary.
And I don't think I get any less done at work than I used to. I'm quality assurance engineer and I don't believe that anyone can really be productive for 8 hours a day in non-trivial tasks.