I have a problem with the laundry service on Princess & we get it free as past cruisers. There're dryers are much to hot & will shrink things like underwear & socks to the point I couldn't use them any more. They washed & ironed my golf shirts alright but any stains were still there until my wife washed them at home & used a little shout before laundering. (if you do use the service bring something to pre-treat items)
I'd use the service again (only in a pinch) but don't expect miracles.