I had read posts on cruise critic about the Gem while it was stationed out of New York, and several negative posts had me somewhat concerned, however, I noticed that once the Gem moved to Venice for Med cruises, posts became almost always positive. Perhaps it was the clientele that each cruise attracted. Embarkation and Disembarkation was not problematic. Our outside cabin was nice, and not too cramped. Cabin stewards were great, servicing us at least twice a day. They added nice touches, like making animal forms out of towels.
FOOD was generally very good. Not everything we had was super, but all our meals were good. Some meals were quite good. The main dining rooms like Magenta and Grand Pacific were good, and if you ordered an entre that turned out to be modest, you could order another entre. The French restaurant was the best, and our meal there was as good as it gets. Also, the Mexican, Italian, Chinese and Japanese restaurants were very good. On some days after a long day ashore, we just went to the buffet at the Garden Cafe, and while occasionally the food was average, you could always get a good salad there. We tried not to gain weight, and eating salads for lunch, if were were not touring (no hamburgers). With all the walking ashore (Walk to the citadel at Nafphlon and the wall at Dubrovnik) and gym work, I lost two pounds on the cruise.
We took excursions from NCL in about half the ports, and were pleased with them all. I had researched on the internet for local tours, and signed up for one at Split (including Trogir). The tour company had forgotten us, but quickly got the tour guide there, and it worked out ok, for about half the price of the NCL tour. We did Dobrovonik, Mykonos and Athens on our own, which worked out well enough. My Daughter and her family got off the tender at Mykonos and took the local boat tour to Delos for a fraction of the price of the NCL tour to Delos. Still, for the tours at Corfu, Santorini, Crete and Ephesus, I thought the NCL tour was the best way to go. Sure, you can do these on your own, but the local tours that I found on the internet were not cheaper than NCL, and doing these places on your own is not easy (you can't see as much if you are not on a tour).
All the staff on the GEM were super.
NCL does nickel and dime a bit much, but if you know that going in, it is not a problem. Don't buy the bottled water, fill up your water bottle from your room, the water is just fine. We spent about $400 on wine, beer and drinks for two for two weeks. In the big picture, this is not huge considering the prices for the cruise itself.
The cruise had many Europeans, and may children, this did not diminish in any way our enjoyment. We lived in Germany for four years, and didn't have a problem with Europeans.
One thing that I noticed after living in Germany several years ago if the proliferation of graffiti, particularly in Venice. It was terrible and much worse than in any American city. Also, saw some in Athens (a little on the islands). Florence was not as bad as Venice, but it curls my hair to see graffiti on 600 year old buildings.
We have read complaints about the internet fees. It did not affect us. We were happy to enjoy the cruise, and didn't need to access the internet at all. One thing that I enjoyed was not having some guy yapping on a cell phone at the next table.