I've sailed on the Gem's sister ship the Norwegian Jade and I really like the size of these ships. I've seen them referred to as Goldilocks ships, not to big, not too small, just right. For some reason I didn't think the Gem had gotten a makeover, but it has. Things on the ship are in good shape, clean and don't feel worn.
Unlike the Jade, the Bliss nightclub has a much better location and it's one of the better night club spaces on the ships I've been on. Again, just the right size. The Gem also has a water slide and a rock wall, which I don't recall the Jade had.
The problem with the Gem isn't the ship, it's Norwegian's approach to it. Norwegian clearly sees this ship as a 2nd or 3rd tier ship, and as such you get a sub-par experience compared to one of their larger flagship ships (like the Breakaway or Getaway).
This cabin is horrible. It shakes and rumbles the whole trip as it's close in proximity to the engines. Worse it's got a hallway on the other side of one of the walls so it's loud all the time. Air circulation in the room was also poor and the cabin felt stuff and stale.