I hesitated to answer because I don't know anything about your itinerary or ports, but I was on the Gem this past March.
The layout is very similar to the Jewel and a little similar to the Dawn. The Blue Lagoon has great wings. The buffet seemed easy to navigate and the dining rooms are lovely. The only thing that we thought was a little odd is the large lounger/bed type things out on the pool deck. There were fake privacy hedges that separated the sitting areas from each other and bamboo furniture.
Is there anything specific you wondered about?