While it may be true that Oasis is more cost efficient for fuel economy than smaller ships, I believe that metric is still based on efficiency per GRT. In other words, the ship still burns more than a smaller ship, but not as much per ton based on size of each ship.
Itinerary planning includes weighing whether it is worth burning the fuel in order to make more shorex revenue vs. onboard revenue. Even whether you go 22 knots vs 18 so you arrive earlier and can offer a few extra tours makes a big difference in revenue. Ships engines become less efficient at top speeds.
In the last conference call RCI said their shorex revenue is a top generator, and so burning the extra fuel is worth it if you sell enough excursions.
I find it interesting that RCI went to such lengths as to carve out a new port in Jamaica as a stop for Oasis (press release):
Royal Caribbean is working in partnership with the Port Authority of Jamaica to complete the new Falmouth Cruise Pier by March 2010, as well as establish the associated infrastructure necessary to welcome cruise ship guests. A historically important 18th-century settlement, Falmouth was a colonial center of Jamaica's sugar and fine rums industry. The town's rich history and Georgian architecture has most recently drawn the attention of His Royal Highness The Prince of Wales, who has been a long time supporter of restoring historic buildings of Great Britain.
Since Jamaica is well-known as a place where you do not want to venture out on your own. Falmouth is close to a well-known river rafting spot; Bamboo rafting at Martha Brae, also close to "Kool Runnings Water Park" and "Chukka Cove's Canopy Tour."
Another stop is Labadee where I believe they have a new zipline attraction that should sell really well.
We still haven't seen much about onboard activities for kids on Oasis, strangely enough. Only one pool so far, no water park announced yet. We know it will have 2 flo-riders.