Mostly this was a great cruise.
The staff are friendly, attentive and for the most part very helpful. The food was great, only one gripe is the sausage at breakfast (avoid at all costs!). The entertainment was great, everything was as you'd expect it to be.
Loved the island visits, these were extremely well organised and made the days a breeze. At no point did we feel stressed or have difficulty organising ourselves, despite being in a large group in several cabins on different decks.
I only have a few minor issues. Serenity is amazing, but was almost impossible to get into thanks to many guests who camped out there from first thing in the morning. They would take two or three pods and a bunch of sun-loungers and then 'guard' these all day, sending others off for drinks and food. Parents with kids looking for an hour or two in Serenity were generally all left wondering around before giving up. Others complained to us that the moment they did find a chair and then went for a swim, their chairs were quickly reclaimed and their towels put on the ground. I know that this is down to guests and not the cruiseline, but there are clear messages stating that pods are only to be used for 90 minutes tops per guest, and this was never enforced. Carnival could easily help to keep this space flowing so that all adult guests could enjoy it, but obviously chose to ignore this problem.
Second (and related) issue was with the family swimming and spa areas. Other reviews have described the spas as 'kid soup' and that's spot on - a spa that could take maybe 6 adults would generally have anywhere up to 20 kids crammed into it, permanently. The kids would be spilling drinks and spitting the water in and out, which quickly stopped all adults from even trying to use them. Again I know this is down to parents and kids, but again Carnival could easily do something about this, but never did. Unless a child was doing something dangerous they would not interrupt, regardless of whether it was disturbing others. One example of this was two children I saw one day spitting down on guests passing on a lower deck, it was up to me to stop them, staff didn't interfere.
Finally, a common issue I'm sure, but we found that the better entertainment (shows and comedy, etc.) required arriving up to 30 minutes early to grab a seat and hold it. Stand up and it was gone, arrive later and you missed the show. Since there's no way to book this, again we found this a bit one-sided. Wiser groups would send in a couple with towels who'd hold a row of seats, and then the rest would arrive at the last minute with all the drinks. If, like us, you saw a show was starting and headed in, you often ended up leaving straight away disappointed.
These issues did detract from our holiday a fair bit. Our kids (aged 8 to 19) all had an absolute ball on this ship, but we found that it was the adults who missed out. Our spa relax time was pretty much non-existent, and we missed a number of shows we wanted to see through not being able to get there early enough.
I do think Carnival lines should address at least the first two points in the future, perhaps taking a little more control of booking shows/using space.
Overall though it was a great cruise, we loved the people, the ship was well appointed and the entertainment (at least what we got to see) was great. Good food, great weather, amazing locations - just let down a little by zero control of guest hogging.