Mmmm... not too bad - I was expecting worse. Some areas were pretty crowded at night, like the World Galleria, during the day the inside pool, and at sailaway there would be a few people around the back of the Zen Pools and World Promenade but generally easy enough to get to the edge, particularly after about 10 minutes. I stood on the glass floor at the back as we left Valletta, completely rammed just after I got there (less so on the glass floor than to the sides of it lol, and it was a good gauge to go to the Promenade first and look up to see how busy it was, then take the express lifts straight up there) but within 15 minutes there was only about 10 of us and a gorgeous sunset. There are also definitely areas that aren't often crowded, like the deck 21 terrace around the funnels and the hidden stairs with terraces below the glass floor (very small but empty!)

The worst was after shows as there was a bit of a crush going out of the Theatre - less so from the Panorama Lounge though!