Excellent all around - our room steward was all but invisible, but always there to clean up no matter how little time we were out of the room - bravo!
Fair to Very Good - Dining room team was just OK; not real personable, but reasonably efficient except for syncing up coffee/espresso/cappuccino with dessert delivery. Had some trouble getting drinks; if you didn't order a drink the prior day, you didn't get asked the next day (huh?).
Food quality was good to excellent (wife liked fish dishes very much); we are not food snobs, but the cuisine on the Magic compared quite well to Celebrity. I am, however, a coffee snob and I found the regular coffee offering virtually undrinkable. I like bold (Sumatra or equivalent) roast coffee and ended up going to the espresso bar to get my morning coffee (@ $1.50 per tall cup) and ordering a double espresso (free with dinner) in the evening (overall, a minor issue).
Breakfast at the Lido Marketplace was very good - had a custom-made omelette just about every day; also, whoever was in charge of potatoes did an outstanding job in both taste and variety of offerings. Had morning room service on a few days and while punctual, on multiple occasions the muffins, pastry or toast were stale.
Barbecue on Promenade Deck (sea days) had burgers, hot dogs, and (beef & chicken) tacos, but no pulled-pork or barbecue chicken - so, a bit of a misnomer. The burgers were very good, though.
The cruise director (John) was excellent - entertaining and informative; best we've experienced thus far.
The entertainment was, overall, the best we have experienced to-date. We went to every evening show (except for the light opera night). We also went to the late-night (uncensored) comedy shows in the Punchline Comedy Club - the ventriloquist was outstanding; the other comics were not quite as good, but funny nonetheless. The live music sprinkled throughout the ship (day and evening) was also of very good quality.
The Serenity Deck is a great option for just lazing around (sea days and other times); however, it was very popular, resulting in difficulty finding a place (circular lounge w/ canopy, hammock, deck lounge chairs) to land. Kudos to Carnival though - they tried hard to enforce the 45min "unattended" rule, removing towels and other stuff when time ran out.
The fitness center was well appointed and I used it almost every other day.
Meeting People / Other Cruisers:
Best by far for meeting people to become social with. Had great dining table mates and also met very nice people on our (non-Carnival) shore excursions.
While I realize Carnival is updating its smoking policy, we can't stand second-hand smoke; every morning, leaving our stateroom, we had to smell smoke (in the hallway) emanating from those smoking in their staterooms. Additionally, smoking was allowed on the port-side of the pool deck (10) and in (and around) the aft bar (deck 10). This is major negative for us and we will be watching Carnival's smoking policy before booking another cruise with them.
The other concern is that, because this was a new ship, Carnival had "stacked the deck" with their A-team. In asking other veteran Carnival cruisers if this was a typical Carnival cruise, we received mixed replies - many said it was the best Carnival cruise they had experience, while (fewer) others said it was typical of a Carnival cruise.
All-in-all, we would definitely do another Carnival cruise, based on our experience with this cruise.