It's an N of 1, but we had a TERRIBLE experience on Norwegian flying home from Italy. Some was just basic flying garbage (flight changed from departing at 7 am to 5 am--makes a little difference in your last night there with kids). They charge you for EVERYTHING. Except clean bathrooms...they just didn't offer those. And after charging us for food, they delivered it at the oddest times (it was really, really weird how they did this--I don't remember the details, I just remember how strange and annoying it was), and ran out of vegetarian, despite the specific order (well in advance of the flight), and strung us out in telling us that was what happened to the point where we couldn't get anything delivered to that child because their food service had ended. Add to that flight attendants who were the furthest thing from service oriented.
I think in the end, it saved us a little money over a major airline, but it wasn't enough to be worth it. Maybe flying as just adults you can accept it all a little better because you're less concerned about the feelings of others, but with a 13- and 11-year old it SUCKED. (The kids handled it fine, but the parents were not happy.)
But the plane was new.
Conversely, we had really good experiences on TAP Portugal (though without the new planes).