I've used it a couple times, but only for DH's dress shirts. (I don't launder those at home, and I'm CERTAINLY not going to do it on vacation LOL!)
Otherwise, I'm too cheap to spend the money, I use the washers and dryers if I really need to. The laundry service is really expensive, as you are charged by the piece rather than the pound. In all honesty, I can only think of maybe three times I did laundry at WDW unless we were in a DVC Villa, which is too convenient NOT to do it!
Anne