I waffled a bit between a 'poor' and an 'average' review, but ultimately chose 'poor' because there were just too many things that we found annoying for our family of four.
First, the pluses.
The cabins are roomy and in pretty good shape. Food in the buffet was reasonably good (with the exception of scrambled eggs at breakfast, which could always be counted on to be cold). Main dining room experience was good at all three of the MDRs we tried. We also tried 3 specialty dining restaurants (Los Lobos, La Cucina, Teppanyaki) and came away very satisfied each time. Wait staff at the restaurants were good. The musical production of Jersey Boys was really first-rate, and having recently been subjected to the incomprehensible productions aboard Royal Caribbean's Anthem of the Seas, this was an unexpected treat. Comedians were funny. And the unlimited drink package was fun, with good pours and experienced and friendly bar staff. So if your goal from a ship is to hang out among adults, simply relax, eat, drink and be merry, you could definitely do worse than the Norwegian Bliss.
The problem is that the Bliss was not the right boat for us. The Bliss has a bit of a structural blind spot: teenagers.
It's not that they don't have a teen club (they do: it's called Entourage, for ages 13-17). It's that the capacity of that interior space is just 65 teens, and on the Xmas vacation week - the time when teens are most likely able to travel - the ship had more than 500 kids just in this age range on it (I can't speak to capacity issues for the younger age categories). Bottom line, unless you line up early, your teen could easily get shut out of the teen club on any given evening. One caveat, some teen events take place in other parts of the ship, but if you can't get into the club initially, it's hard for your kids to connect with the other kids too.
Our kids had mixed success getting into Entourage, but on those occasions when they couldn't get in, the Bliss really does not have a ton of stuff available to them. Unlike the Anthem of the Seas, there's no basketball court or other multi-sport area (doudgeball, soccer, etc.), and there's lip service paid to ping pong (just two tables, on Deck 17 outdoors) and to mini-golf (5 tiny holes, in the middle of nowhere on deck 20). Fitness center? Not for teens. You have to be 18 to use their facility, period. You can't even have a 15-year-old work out with you in the fitness center under parental supervision, nor can you sign a waiver for the ship to avoid liability. We saw fitness staff telling under-18s that they had to leave. Meanwhile, some of the hot tubs (like in Spice H2O) are adult only, and even one of the two pools on the main deck are adult-only. The unspoken message is that teens are supposed to cluster in Entourage, which might be fine on a regular week, but is severely hard on a holiday season week when everyone else with teens is traveling too.
The alternatives for your teens cost extra. Laser tag is an extra $9.95 for two 5-minute rounds, and the racetrack (super fun by the way) is $15 per person for 8 laps of the track. Aside from those things, there's just not a ton to do aboard. Some of the so-called activities were pretty desultory and not well planned. A sudoku event with one puzzle and pencils with erasers that left blue smudges if you actually tried to use them.
It's also really aggravating when the staff are poorly trained. Guest Services would guess where you had to sign up for something and be incorrect. It's a big ship with 4,000+ guests. You can spend a good 10 minutes getting from one place to another. One example. Our teens wanted to sign up for a teen bowling tournament - the ship has two lanes, $6 per game in normal use. We went to the teen club (assuming sign up was there - it was not), who sent us to guest services. Guest services sent us to the box office, where there was a line of people for other things. We waited 20 minutes only to discover that the box office knew nothing about the bowling tournament and tried to send us back to guest services. Come on people. Eventually one of the box office staff took pity on us and made a few phone calls and somehow managed to shoehorn our kids into that tournament. Whatever the 'right' process was, we still have no idea. That was par for the course with guest services.
The port excursions were mostly fine. We stopped in Port Canaveral and Nassau, and obviously trying to move 4,000 people around is not easy and takes time. However, for Great Stirrup Cay, the wind (17 knots) was too strong for the tender boats to function, and so we simply couldn't visit their private island. RC's Anthem of the Seas was capable of docking in the same wind because their nearby island had a deepwater pier, unlike Great Stirrup Cay. That's something Norwegian might want to think about fixing.
If you are a family with teens, you might want to consider taking a trip on the Bliss where you are traveling with other families you know (who have their own teens). We saw a lot of teens hanging out in the beautiful Observation Lounge on deck 15 - a great space - but the point is that having built-in friends to hang with is a huge plus when the normal meeting place for teens (Entourage) might not always be available.
Lastly, the Norwegian app is worth getting for the trip and enabling unlimited messaging, but it has its hiccups. More than once, the app stopped working and wouldn't let us either call or message (sometimes one worked, but not the other). Also, the app is supposed to show next day's activities during morning, afternoon and evening, but we discovered that the app would only do this on the day-of, not the day before. So if you're trying to do a bit of advance planning while on board, the only real option is the printed handouts that arrive around 6pm at your cabins.
Very roomy and bright, well laid out. Good number of electrical outlets for the various devices. Good shower pressure and temperature.
Visited Epcot, fun day.
Could not tender to island due to high winds.