I guess cruise lines are getting with the program!!
I just returned from a 7 day cruise to Alaska on the Star Princess - Princess Cruise line.
Like Celebrity - it seems like the staff on Princess are very knowledgeable about gluten free. On the first day of the cruise, the head waiter met me and discussed my dinner options. Each evening thereafter, he would bring the next day's menus, so that I could pre-order lunch and dinner. When I would show up the next day, I would tell the wait staff my cabin number - and my meal was ready for me. Each meal, while the rest of my family had dinner rolls, I was provided gluten free bread. I was told that any pasta dish could be made with gluten free pasta - and that it was safely prepared separately.
I felt very comfortable eating fruit and cheese from the buffet. There were ample selections to choose from off the menus as well. I packed a bunch of Kind bars - just in case, but I had no need for them.
I ate very well - maybe too well ( flourless chocolate cake, and lots of ice cream!)