It works very well on Princess. There's 1 or 2 laundry rooms on each passenger deck. (Not sure if it's every single passenger deck, but most of them.) Each laundry room has maybe 4 washers and 4 dryers. Probably because relatively few people use the laundry facilities, there's typically no issues with availability. Also I suspect those that do use the facilities use them at all different times of the day. It's actually quite convenient and useful.