The Oasis of the Seas may be the largest ship, but it still felt crowded. The scrum for the buffet was so nightmarish that we only ate there the first day. It isn't nice to make your guests fight for their food or stand waiting for a table while the food gets cold. The promenade was so packed during events that you could scarcely move through it. The elevators were so jam-packed that we would pass several times, often waiting five minutes or more. I also saw several passengers that would push the "door close" button as soon as people exited the elevator to prevent others from crowding in. Many of the passengers were rude, greedy and lacking common manners. (You know who you are.) The crew was obsequious enough to our faces, but we witnessed a few "behind the scenes" crew exchanges that showed a glimpse of the contempt the crew really feels for the spoiled, entitled, well-to-do that they serve. Be aware, they do not really like you - they just want the GRATUITY.
Also, the cruise line seemed to try to "nickle and dime" us every time we turned around. Members of our group had purchased a "soft drink package", but the waiters always attempted to bring a canned soda (costs extra) instead of the fountain soda that was included in the package. You could get a pastry at the Mondo coffee bar, but the coffee there was an extra cost. (Free coffee was available at the Park Cafe a hundred feet away) Some food venues were free at some times and cost extra at others. There was NO coffee available at all until after 7 a.m. (a real trial for us early risers!) Johnny Rockets was an additional cost, and you could not even get your own separate order of fries. They plopped one basket in the middle of the table for "sharesies" for everyone. Yecch!
On the plus side, the shows were superb, and the meals in the dining room were quite good. (It is difficult to eat with "party manners" every night sometimes) The stateroom was comfortable and our cabin steward was really sweet. I am sure his twelve plus hour days cleaning and carrying are hard, but he always had a smile for us.
Here's a hint. Skip Tulum Mayan Ruins excursion. It's a ride to two tourist trap gift shops and a visit to a couple of piles of rocks. Very little in the way of historical interpretation and you cannot get close to the piles of rocks. You can get some nice pictures, but for $89.00, they are pretty pricey pictures.
Over all, I do not recommend the Oasis. They enlarged the ship, added staterooms, theaters, restaurants and an ice rink, but forgot that all those extra people had to visit the buffet and get around the ship.