The startup I work for does this, I work 4 days a week, get paid 5. I love it, makes such a huge difference to have a 3 days weekend, lets you detach a lot more from work.
I'm the CTO and have set up alerts that I get on my phone when I'm not in the office, so even if something critical happens over the weekend it's not like I won't fix it for 3 days.
I noticed that I'm more motivated during the 4 days to do a maximum of stuff, I take less smoking pauses during the day, which increases my productivity and is better for my health ;). I also have no problem to stay one or two hours longer on thursday evening if something needs to be done before the long weekend because I know I will have plenty of time to recover afterwards anyway.
I'm the CTO and have set up alerts that I get on my phone when I'm not in the office, so even if something critical happens over the weekend it's not like I won't fix it for 3 days.
I noticed that I'm more motivated during the 4 days to do a maximum of stuff, I take less smoking pauses during the day, which increases my productivity and is better for my health ;). I also have no problem to stay one or two hours longer on thursday evening if something needs to be done before the long weekend because I know I will have plenty of time to recover afterwards anyway.