I have heard a lot of back and forth on this topic. I'd like to hear from someone who has actually had a positive expereince with this.

My father recently found out he will be working 8-6 four days a week. His company is doing a trial period where all the employees work four days a week and rotate getting Monday or Friday off. It's nice that he gets three day weekends now and can save a little on gas money. I don't know if this is helping the company overall, but it seems to be helping the individual employees!

I have a web design firm and we bill by the hour, so we'd have to get 40 hours in four days. I know when we've worked 10 hour days consistently, productivity lowers. Its productivity that makes my business and the economy run. I don't believe cost cutting is the solution, rather it is producing more and better product. I'd like the idea of a day off for golf though!

I consider this a great idea, this idea also reduce the amount of times that employees need to request a day for personal stuffs and most get more happy of getting an extra day off even if they work a little more during the week, but this is not for every business.
Another variant to this is to allow people from some departments to work from home 1 or 2 days a week, I worked for a company that employees only go to the office 1 or 2 days a week for employees that passed a trial period and demostrated responsability. This office saved a lot on space in the office by having general spots for the moment an employee was there and meeting rooms, they also saved a lot in office supplies and energy.
This option is also not for every business.