We have cruised over 10 times, mostly from the West Coast USA on medium sized vessels. We decided to go for broke and book on the world's largest ship.
I'm not sure I can ever go back to a smaller, lower class vessel, we were absolutely blown away by Oasis (OOTS)!
Flawless check in; the vessels various 'neighborhoods' (i.e Boardwalk, Promenade, Central Park, Solarium) are separated so the passengers are dispersed all over the ship , it never felt crowded. Where else can you take a midnight walk in a living park under a full moon?; an abundance of deck space, pools, jacuzzi's and chairs, towels are provided free; big thumbs up for specialty restaurants Solarium and Giovanni's Table (BUT, see comment below about Chops Grill); the entertainment is top notch, professional, and varied including the Aqua Show, Ice/Aerial Show, jazz, special guest performers, comedy. This is not the typical lip syncing song and dance crap found on most ships; easily the largest, best equipped fitness center on the seas, towels provided free (exception is the cardio machines, see below); zip line, golf, rock climbing wall and flow riders are all free; outstanding children's programs, they completely engage and educate the kids (which selfishly keeps them out of the public/'adult' areas), we saw many children crying not wanting to leave the children's area when their parents picked them up; a welcome obsession with cleanliness, lots of sanitizers and staff dispense it mandatory at the buffet entrance; and, attentive staff, very available but unobtrusive and not continually hawking you to buy drinks/packages, etc..
We have many more accolades but a few negative comments about OOTS:
1. The Chops Grill: Amazingly bad: poor unprofessional rushed service; limited menu, and after paying the $35 specialty restaurant premium, they want to tack on additional charges for steaks; the steaks (including fillet mignon) were tough, over seasoned and tasteless;
2. The buffet had limited hours, add more flexibility to late night dining options.
3. The cardio machine's digital, interactive screens and programs were all faulty and mostly non functional. Definite design flaw.
4. The room has a big flat screen, great. But should be set up to pair with your device (laptop, mp3 player, etc.), and im'ing between rooms would be a welcome addition.
5. Departing the ship in Fort Lauderdale was a disaster, it took hours to get through customs.
When can I go again!?