This is a long review. I feel like I got a lot of great information from other detailed reviews I read on here so I'm trying to pay it forward.
Backround Information - My husband and I are 27 and 26, in our first year of marriage, no kids. He is a first time cruiser and I went on one as a teenager with my family.
Ship Info - Carnival Magic is huge. There seemed to be lots of elevators to get you up and down. We took the stairs most of the time because we didn't want to wait for the elevators. There are two rather small pools and lots of jacuzzi tubs. The pools were usually full of people by lunchtime. We spent more time in the jacuzzi tubs because we could usually find one that wasn't full and because they were kept at the perfect temperature. Never too hot. There is a cool pub called Red Frog Pub that is apparently the first one on carnival ships. They have their own beer, bar games, live acoustic music. My husband and I enjoyed hanging out there. The serenity deck (adults only) was nice. We could always find a lounge chair available there. The loungers by the beach pool were usually pretty full by lunch time.
Activities - The two waterslides were both fun and the lines were never really long. The ropes coarse was a lot of fun and a little scary at first. There were at least two adult dodgeball tournaments during the week. We got there a little late the time we tried to join. It looked like a lot of fun. We were sad we missed out.
Service - Our waiters at dinner were very nice. Always friendly and smiling. Overall I felt like all of the employees always seemed happy and like they really enjoyed their jobs. The only day we had exceptionally bad service was our last day at sea. We went for breakfast in the dining room (which we did most days). Our service was terrible. We waited so long with empty water glasses that my husband finally got up and grabbed the water pitcher. That got their attention and someone came running right over. After that we still waited a considerable amount of time for our food, as did the two tables next to us. That was the only time I can think of that we had poor service.
Stateroom - We were in room 7440. We booked on the 7th deck based on the ship review on this site. It was a very quiet deck as their aren't any dining rooms, show rooms, clubs, etc above or below it. We had a balcony room toward the back of the ship. It was great. Plenty of room and storage. The balcony had two chairs and a small table.
Dining - The food was mediocre with a few exceptions. We only ate at the lido buffet a few times and weren't very impressed. Beware of powdered eggs at the buffet. We tried the mongolian wok on our first day and it was just ok. We went to the punchliner comedy (sit down) breakfast on the 3 sea days. We enjoyed the huevos rancheros, breakfast burrito and omlettes. One of the comedians told a few jokes every hour. Dinners were ok. The standout dishes were the escargot (we ordered extra because it was so good!) and the lasagna. We went to the steakhouse one night for $30 per person. The atmosphere was nice and most of the food was delicious. I'd definitely recommend the ribeye over the surf and turf. On our last night we decided to try the italian restaurant that is $12 per person. It was wonderful! The atmosphere, staff and food were top notch.
Drinks: Most cocktails on the ship were $8.75. We thought that was pretty expensive considering the cost we had already paid for the cruise. One money saver is the drink of the day - usually $1.00 less and you get to keep the cup. I think it was $6.75 to get the cup refilled with that drink. Every bar made a great mojito, which is one of my favorites.
Entertainment - We did not go to all of the shows or events. We did go to two comedy shows and enjoyed them both. I recommend arriving a little early to make sure you get a seat. The hairy chest contest was really funny. We went to the murder mystery show and were pretty disappointed - probably only worth your time if you have kids. The game of love and battle of the sexes were pretty funny.
Photography - When getting off the ship be prepared to be bothered by carnival staff to take pictures. You can wave them off or keep walking. We didn't take any of those pictures but we did take some on one of the elegant nights. We found out the next night that they wanted $20 for each 8x10. We think that price was crazy and we didn't buy any.
Port and Shore Excursions - We booked three excursions through carnival.
Montego Bay: We were very unhappy with the first one. We went on the Chukka Horseback Ride and Swim. It was supposed to be from 9:30-12:30. We waited and waited in the hot building at the port. Then they took us outside and we waited some more until our bus finally came to pick us up. The horseback ride was very nice. There are some beautiful views and at the end you ride along the shore back to where you start. Then we did our ride into the water on different horses. Our ride in the water was significantly shorter than the group we watch ed before ours. We were pretty disappointed that they rushed that part. Then we sat and waited for around an hour until our bus showed up to pick us up. We didn't get back to the port until 3. We had planned on having about 4 hours after this excursion to go to a beach and were very disappointed that instead we spent 3 extra hours on this excursion waiting. Also, they have lockers to secure your things but they charge you $5.00 to use them. We enjoyed the horseback riding a lot but were very disappointed that we spent most of our day in Montego Bay waiting. We complained at the shore excursion desk. I didn't find them to be very helpful. They refunded 20% of our excursion cost. On a positive note, our bus driver, Garfield, was wonderful. He gave us some great info about the island and kept us laughing.
Grand Cayman: We really enjoyed Grand Cayman. It was beautiful there and I would love to go back. We booked the Stingray Encounter and Turtle Farm and enjoyed them both a lot. We took a bus ride the boat that took us out to the stingray sandbar. The ride out to the sandbar is nice. They gave us info about how to handle the stingrays while we were on the boat. Once we got there I was a little concerned because there were already a lot of boats out there but there was plenty of space for us and we had plenty of interaction with the stingrays. Our guides did a great job making sure everyone got to hold, feed and kiss a stingray. We brought a waterproof digital camera and got some great shots of the stingrays swimming around us. We got back on the boat and went back to shore to get on our bus to head to the turtle farm. I wished our bus ride had included some info about Grand Cayman but I don't think the bus had a microphone or anything of the sort. When we arrived at the turtle farm we were quickly put with a guide who walked us around the different tanks of the farm and gave us some great info about how and why it started. My favorite part was definitely holding the 1 year old turtles. You can also go snorkling in their lagoon but honestly that wasn't too exciting. There were very few turtles in there and you aren't allowed to touch those ones because they are getting released into the wild.
Cozumel - The port area in Cozumel is very nice with lots of shops. Be aware that the prices will be lower if you cross the street for souvenir type things. Also, be sure to bargain because they will lower their prices. The food is great. We went on the Beginner's Scuba Excursion. We waited quite a while to get all of the people gathered and then for taxis. This excursion does not use their own bus. They put you in taxis that are included in the price. You sit in a short class about the basics of scuba and then you dive for about 25 minutes from the shore. The dive was great. It was a fake reef I guess you'd say but there were lots of beautiful fish. When you're finished you can stay as long as you like and snorkel. When you're finished they will pay for a taxi to take you back. We had some food there and it was delicious. Also, they have lockers for your bags that are $2.00 to use.