Aloha From Honolulu,
I've been on two NCL overnight cruises to nowhere here in Hawaii, one on the ALOHA in July of last year and just last month on the AMERICA. Both of these cruises were charitable fundraisers each raising over $400,000 for local Hawaiian charities.
They can be alot of fun. The biggest let down was that we only got 3 meals. Especially with the Freestyle dinning set-up and the variety of available restaurants, you feel like your missing out. If it is a single main dinning room arrangement that wouldn't be an issue.
I enjoy Weekend cruises much more, you get a chance to settle in and relax. I've done Carnival's weekend / 3 day cruises out of Long Beach to Baja Mexico and they are a lot of fun.