While I am a seasoned cruiser, this was my first RCI experience. My usual choices are Oceania and Windstar and while those lines have much smaller ships, my issues with Oasis were not necessarily based on its size, rather on the service.
Cabin Housekeeping. There was not one day that the room was cleaned and stocked properly. Every day a call had to be made for glass ware, towels, the daily calendar, more room service hang tags, etc. I have no idea what we were missing that we didn't know to expect (ice, pen, paper to write notes). Usually when we called for supplies we got them promptly, but once there was no answer and once the attendant told me he would get me drinking glass in 20 minutes. It took much longer.
Food Service. Our dinner service in the main dining room was flawless. Service and food were want we expected. Service and food in other venues less so. Food was frequently not hot when it should be and not cold when it should be. Tables were not bussed promptly causing people to mill around with trays of food looking at empty tables piled high with dirty dishes. The Solarium area is for 16+ patrons but was frequently occupied by toddlers with their parents. The staff did nothing to enforce the adult only policy.
Best loation on the ship. Deck 8 is Central Park, and the cabin is just off the aft elevator lobby making it convenient to most locations.