I'm not one for long, detailed, day-by-day trip reports, so I will just give a quick summary and thoughts on each of the different aspects of our cruise.
Our info: Family of 4 from NYC - myself, the wife, and two teenagers (son 17 & daughter 14). 12th cruise overall. 6 on
DCL, 3 on RCCL, and 2 on NCL, so this was our first on Carnival.
Cruise info: 8-nt Southern Caribbean on Carnival Horizon out of Miami. We booked a Family Harbor Suite (deck 2) stateroom.
Flew into FLL the day before the cruise, spent the night in a Hampton Inn (big fan of Hampton Inns for these type of overnight stays) near FLL and the front desk arranged for a taxi to take us to the Port of Miami at noon the next day. Was planning on just getting an Uber, but they quoted a reasonable price, so we just accepted it and it worked out fine. Got to the port, dropped the luggage with the porter, and went to check in. A Carnival employee outside asked to see our boarding passes, saw we were in a "suite" and said we could go to the priority line (didn't know or wasn't expecting that). I had done online check-in, so apparently there really wasn't anything to do at the port. A women checked our docs right before the security screening and told us our cards were waiting outside our room and that our room was ready (it wasn't). But it was already a little past 1pm, so it was only a short while longer. We're not ones who always try to be among the first on the ship - particularly for non-DCL cruises. We'd rather have a leisurely morning and check-in after the rush has settled down and we won't have to wait too long for our room to be ready.
Stateroom (2433 - Family Harbor Suite) : Loved our stateroom. Good amount of room, and plenty of storage. Long cove balcony with 4 chairs and 2 tables. The DCL-style split bathrooms, but with two showers, really came in handy. Our stateroom steward was great also. Was a little noisy with I guess the galley right above us, which may bother some, but not me. I guess that's a result of living most of my life within a stone's throw of JFK airport.
The Family Harbor Lounge, however, was a huge disappointment. First off, I thought it was supposed to be open24/7. It was not. It was closed probably by 10pm. The breakfast buffet was fine in there for the limited space they have. After that though, it was pretty useless. Some snacks (potato chips, tortilaa chips & salsa, PB&J, etc.) in the afternoon, and some cookies in the evening. That was it.
Food: What a pleasant surprise! Pretty much everything and everywhere we ate exceeded expectations. The MDR (Meridian - we had Your Time dining) was excellent each of the 3 nights we ate in there. Portion sizes were a bit small, but you could always order more. We ate at three specialty restaurants (steakhouse, Italian, and smokehouse) and all were outstanding. The standout was the steakhouse. Incredible meal - as it should be for that upcharge. We got the package they offer for $60 which includes the steakhouse (normally $38 pp and two $15 vouchers that can be used at the Italian restaurant ($15 pp), the smokehouse (a la carte) and I believe the Asian restaurant. So $60 for a $68 value. Only got a guy's burger once. It was good, found it very similar to Five Guys, so not sure what the craze is about. The pizza place was just okay and they were constantly running out and people would be waiting around for the next batch to be done. Didn't get anything from the seafood shack or taco place. As for the buffet...a mixed bag. The selection/variety was far less than I have seen on any other ship. That said, whatever I did have was fairly good for buffet food. Two things at the buffet though not related to the food - first, it was always insanely warm in there (this was a theme throughout the ship, seemed everywhere except the main theater was lacking AC), and secondly, the floors were always very slippery.
Entertainment: Saw 3 of the 4 production shows. Obviously, this is the one area no one can match DCL. The performers were actually pretty good, but the shows themselves were just...meh. They were all just singing and dancing - no dialogue. They'll tell you there is a story to them, but I doubt anyone else would agree. Saw a lot of the comedy shows. The comedians were all very good. Love & Marriage show...we've all seen this done before with the same exact formula - three couples (one older couple, one newlywed couple, and one in between) in a "Newlywed Show" type of game. Still, always good for a few laughs. What was a first for us...The Quest. Wasn't sure what to expect going into that, but we sure had fun. Liar's Club was also very funny.
I've always been someone who never understood why people would ask about certain cruise directors, but I do now. Mike Pack was amazing. I don't know if I've ever seen someone with that much energy. He was EVERYWHERE., and hosted EVERYTHING. Often times, a CD would mainly just introduce the feature shows for the night and make some announcements during the day about what's going on. Not him. He would literally go from one event to the next all evening long. He was out on the pier at every port, welcoming guests back. Glad we caught him on his last cruise before vacation (which will include his wedding - so congrats Mike!).
The ship: Overall a beautiful ship. Biggest issue was the casino. They saved me some money because I couldn't set foot in there the smoke was so bad. It was incredibly difficult to even just walk through. It's on deck 4 - same as the theater (forward) and the comedy club and sports bar (both aft). So if we left the theater, and wanted to go to the comedy club, we would have to go up to deck 5 and then back down. Very poor job ventilating the casino. Okay, that was probably the second biggest issue. The first, is clearly the infamous elevators. I suppose if everyone used them properly, they would be more efficient. However, that was far from the case (I doubt it ever will be) and it was just a disaster. You waited forever most times. I think most people failed to realize if you have 4 people, you need to press your floor 4 times. So the "smart" system often though it was sending you an elevator with plenty of room, only for it to be full. Gave something for everyone to commiserate over (and provided material for all the comedians).
Lastly, a comment on the "Carnival Crowd". If I said I didn't notice a difference from all our other cruises, I'd be lying. There apparently was an incident where a girl from the 15-17 year old group got jumped and beat up by a large group of other teens. I asked my son about it and he pretty much confirmed it, saying while he didn't see it (was watching the midnight movie on Lido) , he had heard all about it. Never heard of anything like that on our previous cruises. Would it prevent us from sailing Carnival again? Probably not. But there definitely is a difference.
I'm sure you'll have an amazing time! (I'm quite envious) I hope you'll post pictures when you come back.
(For lack of better words) 
