I haven't been on the Holiday although my hubby's coworker and customer did just get back from it two months ago and had a great time. I have been on her sister ships the Celebration and the Jubilee. They are the exact same ship but different colors on the interior. The very back cabins have a lot of vibration but the very back ones over the wheelwash are also almost twice the size of the normal outside cabin. We always pick those on that ship if possible. Look on the Upper deck or "U" in the brochure in the back. I think it is the same on the Empress deck too. The ships are a little cut up as in some floors do not go all the way through because they are blocked by the dining rooms. Not a problem just confusing sometimes.
Only carry about 1400 people so they are a lot of fun and the people seem to mingle more than on the bigger ships. We love the very front of the ship - walk through the sports area also known as the topless deck to the very front in front of the windows - it is great to sit on the window sills and nothing in front of you but ocean!
The Mississippi can be a bit rough so the boat will move a little. We love the cruise down the Mississippi - lots of oil rigs and stuff on both sides of the river. If you can stay up and watch it is not normal to sail on a river..
If you like sushi they usually have it down the boulevard area of the ship where the casino and clubs are around 5pm. The piano bar is by the restaurant in the middle. It is a fun place too. Any specific questions I can answer email me..