I flew BOS - LGA RT in May 2018. Things may have changed since then but here are my thoughts on Norwegian Air.
As I recall it was supposed to leave BOS around 8:30? Everyone was just standing around the gate area. There were no announcements of any kind. Seemed to be something to do with passport control on a few passengers? We were about 45 minutes late boarding - with no explanation. Seemed disorganized.
Paid for Premium - it was a good deal! But the seat was not very comfortable and you really are stuck when the people in front of you recline their seats. Almost impossible to get your bag stashed under the seat in front of you, out, without crawling on the floor.
Had a nice dinner at the airport before I left on both legs. Airport lobster on the way over and Wagamama (Asian food) in the Gatwick airport. I had not read stellar reviews on Norwegians meal offerings. Even in Premium it came in an oblong box and you pretty much ate out of the box. I DID have a roll because you could actually smell fresh baked bread! Not sure how they did that but the rolls were great! Looked like the meals were sort of like a Lean Cuisine with a salad and a dessert. My seatmates on each flight were finished quickly.
The Premium seat was wide . . and the recline was good but on the way TO Gatwick I was very uncomfortable. You get a blanket but no pillow and I really needed something behind my back. There is a leg rest and a foot rest. TIP** There IS a button to extend the footrest that I did not find until the end of the flight. It was in the left hand armrest. Ask if you can't find it. I had my pillow out on the return as well as water and snacks (see below) and it was a much nicer experience.
The entertainment was very extensive and responsive although the earbuds were uncomfortable. Cheap.
SO . . . cant speak to Economy. I guess you just hope the flight is not full? Are you flying on the Dreamliner? Nice jet.
If I were to fly them again
1. In Premium I would pick a bulkhead seat.
2. I would bring my own earphones.
3. I would bring a pillow for my back OR be sure I had a cushy coat to roll up.
4. BRING YOUR OWN WATER! Even in Premium we only got one 16 oz bottle.
5. Bring snacks. Nuts, string cheese, crackers, . . . . .
6. Have the stuff you want for the flight easily accessible - like in one big Ziploc that you can pull out of your carry on just the one time.
6. Take a yoga class.
The flight attendants on my two flights were efficient but not overly chatty or friendly. And they pretty much disappeared (quietly) between the meal service which is why I would suggest bringing your own water. I read this somewhere else, too, that water was hard to come by.
Also the Gatwick arrivals terminal didn't really have a lot to it? Not many places to sit and no sit down restaurant. I grabbed a sandwich from Tesco's or something, waiting for rush hour traffic to be over. Also you can take a "normal" train into London, you don't have to take the Gatwick Express.
You can't beat the price, especially if you are doing a one way. It's a low cost airline and felt like one, even in Premium. But it got me there mostly on time and was not horrible. I would not hesitate to fly them again on short notice (to make sure they were not going to go out of business) but waiting to see what happens with them financially.
The weeks before my flight, Norwegian was cancelling MANY of their trans Atlantic 787 flights so I was stressed out.
Have fun on your spontaneous trip!