We where on the NCL Pearl 3 times in 2007.....
We were on the Jewel in 2006..both beautiful ships.
Both of these ships are sister ships of the Gem....
We will be on the Sky in March 2008....
Also several others in the past, older ships like the Dream which is now outr of the NCL fleet. NCL booasts to have the youngest fleet of ships cruising the oceans.
Our favorite was the Jewel and of course the Pearl. The Jewel, Pearl and Gem, all have the grand buffet setup with food stations that we thought was a great concept. We also like to take in Teppanyaki, and we usually do that the first night out of port...as our NCL cruise consultant usually provides a coupon book, that gives us the first night out at a specialty restaurant 2 for 1. Pearl, Jewel and Gem have multiple pools.
I have sailed RCL and Princess many times, we still favor NCL for all the reasons you discussed, causal dress and we love the Freestyle approach to cruising. For us, it's what we like, for others, they would rather have the more regimented style of cruising. I truely do believe that NCL has set a standard for relaxed cruising for those who just want to have a good time overall without the formal nights and fancy tux's.
We did however enjoy our 15 day cruise to Hawaii last year via the Diamoond Princess. We did find it was an older age of passengers. I was on the Diamond Princess three weeks after it first sailed, and three years later. When on again, I felt it needed a lot of work to bring the ship back up to conditons as new.
One thing we find about NCL is maintainence is a top priority.
Glad to hear you had a great time.