As long as you don't have super long, thick hair, the hair dryers onboard will do fine. I sure like the idea of not having to pack one, you may want to just in case, especially if you have one of the travel ones that Pam was referring to?
I found out firsthand that the on-board dryers don't work too well. We had the same kind in Italy--attached wall-unit thingies w/ a plastic hose--only 800 watts. The one I use at home is 1800 watts (!) I spent most of the cruise with my hair in a damp ponytail, which, given the Alaska weather, never fully dried all week.
Ladies, take heed: bring your own travel dryer for shoulder-length hair or longer. Eliz wrote: