Love this class of ship. I was just on the Serenade in Feb and also on her last Feb too. Deck 4 is fine. That's where I was this last cruise. Actually it's great because you can slip down and be in the Centrum, which is where all the activity is happening, in a couple of seconds. I like being closer to the front elevators because they aren't used as much so you can get an elevator quickly.
The food was good. Didn't eat in the Dining Room much but the food in the specialty restaurants was excellent.
I have yet to get good coffee anywhere on the ship -- any ship! But that is also a matter of taste. Some like it strong, others weak, but I think the room service coffee is the best for my taste. And the Lattes in Latitudes is wonderful!
My favorite thing with RCL is the staff. Very rarely do I run across someone with a bad attitude. They are usually very helpful and do it all with a smile. Not all, but most.