Service - I don't think any of the reviews I read criticized the service, that's because the service was wonderful. The staff are mostly young energetic people from many different countries. They're well trained, they care and they're interesting people. I really enjoyed meeting them.
We chose concierge class, but I wouldn't recommend it. I'm glad we had a room with a balcony, but you can get that without paying extra for concierge class. The flowers in our room were limp after a few days and not changed, the fruit was just a couple of apples and an orange, the afternoon snacks were a few olives, some peanuts, etc. - you're so full all the time from the wonderful meals, you don't need extra fruit and peanuts. We had a bottle of champagne in our room that we didn't even have time to drink.
I thought the food was great. If you want to go to the Ocean Liner restaurant, go early in your trip and you'll get a pretty good discount. We liked it so much we went later in the trip also. We also ate at the Tuscan Grill and had crepes at the bistro one evening - all wonderful. The main dining room was excellent also. We mostly only ate breakfast at the cafe. We always found plenty of things we liked. The ice cream was not that great because it tended to be crystallized, but the gelato on deck 5 was great. If you go at 4:00 pm you can get 2 for the price of 1.