I stayed in one on the Navigator. All Pros, no Cons that I can think of. They have more room, a good view and he balconies are nice. It's worth it.
Sovereign of the Seas 2/03
Navigator of the Seas 2/04
Adventure of the Seas 2/05
Serenade of the Seas 2/06
Monarch of the Seas 7/06
Liberty of the Seas 8/07
Majesty of the Seas 5/08
If you have a RCCL brochure, look at the deck plans (or you can do the same thing on the website). Approximately in the center of the ship, the outer walls bulge out into a "hump" or "bump". These cabins are the same size as other balcony cabins in the same category. Some of the balconies are larger.
We've had these cabins several times, and prefer them to "ordinary" balcony cabins. Since they are approximately in the center of the ship, they are convenient to stairways, elevators, the Internet Cafe, Library, etc.
Other than giving the ships a distinctive look (compared to other cruise ships), these "bumps" don't seem to serve any practical purpose.
Serenade of the Seas b2b January 2016
Serenade of the Seas b2b January 2017