Norwegian offers breathtakingly low prices and brand new planes. In general, the flight operations are good -- they take off on time and land where they are supposed to.
However, baggage handling can be a huge problem. Norwegian's business model is to severely limit carry-on; this speeds boarding and increases their revenue for baggage fees, OK. But when flying into the US (I've experienced this at both Oakland and Boston-Logan) they use contract baggage handlers who could not care less. I've had 3 flights in the last year in which 100+ people were waiting for bags more than 2 hours (yes! 2 hours!) after the flight landed.
Try to find someone who can help? Good luck with that. The airport staff say "ask the airline" but of course you're quarantined behind the customs agents and can't talk to Norwegian. When you get out and ask Norwegian's check-in staff "What happened?" they disclaim any responsibility for arriving baggage.
I've twice filed complaints and had irrelevant responses (e.g. "Maybe the plane was late," or "Sometimes weather . . .")
I've vowed I'll only fly Norwegian again on short trips where I can carry on what I need.