The hairdryer is adequate but not that powerful. Still better than dragging one along in the luggage. As far as shampoo and conditioner, I think they had the combination on our last cruise. And Princess uses those cheap cardboard containers instead of the nice plastic bottles the better hotels have. They are difficult to tear open when one's hands are wet in the shower. It's probably the only gripe I have about Princess.
Princess has shampoo, conditioner (not 2-in-1), hand lotion and a hair dryer in the room. As part of Princess' commitment to the enviroment, these items (with the exception of the hair dryer) are packaged in bio-degradable cardboard, not plastic. While they may not be as attractive as the plastic, consider how many thousands of these items are discarded on each ship weekly and you can begin to have an appreciation for their commitment to reduce plastic waste.
We were on the Grand Princess last month. Plenty of shampoo, conditioner and hand/body lotion were provided. They are packaged in cardboard containers; not hard to work with, we weren't offended that they were not packaged in plastic bottles. The hair dryer didn't have a lot of power; if you have long and/or thick hair, you might want to considering bringing your own hair dryer. No extras, sorry. Pack anything you feel you might need. I forgot aspirin. Bayer Aspirin, in the ship's gift store, was $1.09 for 4 tablets! Tampax was $3.75 for a box of 10.
one of nice extras that are available are terry cloth robes, if they are not in your cabin, ask your cabin steward for them(free of charge) I always bring my own hair dryer, i have found that the ones in the cabin are not strong enough, and i don't want to spend 1/2 hr trying to dry my hair with a weak hairdryer. The shampoo and conditioner are about the same as any basic ones you would find in the drugstore. If your hair has special needs, bring your own. If your hair tends to get frizzy in the humidity, then bring a silcone-based, anti-frizz product. Forget about hairspray, that is unless you don't plan on going outside.