Well ive never been on a celebrity cruise before but just looking at the comparison in port shes quite a bit larger, One problem I ran into on the grand was that i got lost quite often. But my biggest problem was that my room was in the bow of the ship and my dining room was in the stern, so it was a hike every day to dinner or any other meal in that dinning room. When you get on board you will have a small guide (or at least I did) that says "grand princess pocket guide" this will come in handy. Each floor has its own carpet pattern this might get confusing. Well I hope that this post helped you in some way, shape, or form.
Hope you have fun