I went on the Carnival Dream over New Years (Dec 09 into Jan 10) and just went on the NCL Jewel this past July. I loved NCL, the Freestyle dining was awesome. Not having a set dining room time was great because it wasn't like I felt I had to work around an 8:15 dinner which I did have to do on Carnival. Both cruises I've been on was with groups of 13 and the freestyle made it very easy. Also, the specialty restaurants on NCL were incredible. We did Teppanyaki which is Japanese where they cook in front of you, did an Italian restaurant, ate in the main dining rooms a few nights, etc... It was great because being able to get dressed up and take the girlfriend to one of the specialty restaurants made it feel like a vacation on a vacation. I loved NCL so much a few weeks after I got home we were already looking at another cruise and within a month booked an 11 day Southern Caribbean on the Dawn over Thanksgiving out of Miami.
I did have a good time on Carnival, but I had such a better time on NCL and would definitely recommend that to anyone looking to cruise. The freestyle dining is a huge selling point for me. Even if you don't do the specialty restaurants and just do the main dining rooms, I just really enjoyed being able to eat when I wanted, and not be assigned to a specific dining room, table, and time.