NCL is my cruise line of choice these days. It is not the most luxurious nor is it the most economical, but it is a solid cruise line that appreciates casino players. I have been getting comped cruises from them now for several years, and I am not a high roller! After taking your first cruise with them, even if it was comped through CET or another casino. I highly recommend calling their Casino at Sea department to see what you qualify for on a future cruise. You should always ask about a specific ship and date, as their offers vary (a lot) depending on ship, itinerary & time of year.
They also sometimes offer additional specific cruises for Slot Tournaments or other casino events which they do well. Their casinos are always humming and lots of fun. Although the selection of slots will never rival a land based casino, their larger ships in particular have a really good selection. The casino hosts are friendly and visible and often offer additional discretionary comps such as dinners in the Steak House. If you book through Casino at Sea or a land based casino, cocktails in the casino are comped, and that is not the case in general at sea. I confess to spending way too much time in their casinos HHH
I have 15 cruises with them on 9 different ships, and I think their loyalty program is decent. Along with all the worthless perks like priority boarding, they give bottles of wine, a specialty dinner with wine, free laundry (sounds like nothing but it's really nice to have) and some other stuff I forget at the moment. They don't have the preassigned dinner seatings on their ships, and do everything Freestyle. They also have a very casual dress code, which I really like. In their new bigger ships, they have some exceptionally good entertainment. One of the ships has Blue Man Group, and a couple have Howling at the Moon piano bars and a great Blues Club. And of course, all of the regular cruise ship shows. Their martini and margarita tastings are A BLAST!!
If you are cruising solo, and you book through the casino there is NO SINGLE SUPPLEMENT. That can be a huge savings by itself!
I could go on and on, but also can get carried away. If you have any questions about NCL, fire away!