I'm sure this should appeal to experienced cruisers like Kantwait2crooze who lamented in a previous thread that the NCL ships were now too large, and still felt overcrowded. They could win back or capture some of us who are starting to feel like the newer ships lack intimacy. No to mention that getting around on those monsters is starting to feel akin to walking through huge airport terminals.
Their rational of being able to stop at smaller, out of the way ports appeals to me. There are a lot of places I'd like to see that are off the beaten path and subsequently off of a lot of peoples radar.
Also, sticking to longer sailings should eliminate a high percentage of the younger, more boisterous crowd as well as family's with small children, simply because the longer sailings will be financially out of reach for a lot of them.
Personally, I believe this concept will succeed as long as they can keep competitive price points with the other majors offering the same length sailings. Otherwise their market share will be eroded by the behemoths (CCL, RCL, and MSC). Time will tell.