First trip with Royal Caribbean; Serenade of the Seas is a fine ship, meticulously clean (and I am a bit obsessive)with an accommodating service staff. It was terrific that we were at the pier in every port so dory transfer was avoided. This was particularly important as we made our own shore trip reservations through shoretrips.com and some of the meet times were early. Highly recommend that site.
Had a balcony cabin, and was happy with it. You don't get more cabin than one with a large window, but it was worth the up charge to have breakfast on the balcony a couple of times and to watch the sunset with a cocktail and room service snacks. The room service food was just OK, not as good as either the buffet or the dining room.
Menu selection was well varied in the dining room and had some well prepared offerings. I purchased a 12 bottle wine package the first night for $300, and it turned out to be the disappointment of the trip. The first wine ordered from the package list was not available. The replacement offered was poor, which was replaced with another which was acceptable. I love wine with dinner, and don't spend a lot to have very good wine. I am used to restaurant pricing of 2-3 times retail; this was 4-5 times. I have brought my own wine on other cruises and paid corkage; not an option here, even from the on board "duty free." That is true for you room as well: can only order from room service.