We just came off the Gem and had an opportunity to sit for a private photo shoot. It took about an hour, and, granted, many pics were not satisfactory. However, we did create two triptychs. One consisted of three separate images. The other was one image, broken into three frames. We look forward to receiving the finished prints in about 4-6 weeks.
If you are beyond the usual souvenir hoarding stage and want a great memory, I strongly suggest you try a session. You may also want to consider a custom bobblehead. They are really cool too. Expect to pay a decent amount for the high end photos, but to us, they are worth the effort.
Let me add, by unsatisfactory, I mean that we didn't want to use them. It was about us and positioning, not the skill of the photographers. They are amazing and often get a bad rap for working on a ship. These are actually some of the best photographers you will run into.