I worked 4 days for years and i loved it. No down side at all for me. Great if your going away for the weekend since the Friday doesn't need to be taken as a holiday. O/T on a Friday at 1.5x was better than doing Sunday at 2x.
It was only the manual staff that did it, ie the workers, where the office staff did the normal hrs.
Staff did the 5 days since they had to man the phone etc for clients phoning in.
Finally got stopped due to certain staff moaning all the time about it.
Told them to put a boiler suit on and join us on the shop floor if they wanted a 4 days week
Of all the different shifts that i did, 3 shifts, days &nights, 5 days, the 4 day week was the best.
It was only an extra 1.25hrs per day for 4 days to make up the 5 hr Friday.
If you get the chance, take it.