Also do not forget that for now---
DCL only has 2 ships, high demand and no casino. That is all reflected in the price. They do get some decent deals every now and then.
It's all relative though as to what is important to you.
We did a 7 day Carnival and a 4 day Disney within the same month. While Carnival is not my or DH's cup of tea, I was very surprised at how much my kids truly enjoyed Camp Carnival. They really did get to know their counselors and make friends.
We didn't feel that way on Disney--even though my kids loved it as well. I think they liked the branding, but truth be told, we got more "oohs and aahs" out of the Camp Carnival Experience.
I don't know why that is other than perhaps there was just so many kids on DCL (regardless of time of year). I know you will get folks who will state how wonderful the counselors were and that they knew their kids. We just didn't get that same warm fuzzy. I think it is hit or miss based on numbers and the personality of the child.
If you like Disney--you will most likely like some aspects of the cruise.
Whether or not it was worth it is a decision that only you can make after you have actually done it.
I intend to go on DCL again--but I'm not one of those that was "Wowed" either. I just enjoy Disney and would like more time on the boat. I do not envision us being frequent sailors though.
From a parent standpoint--I found Flounders hands down to be the most fantastic option as I sailed with a baby. Carnival only has babystting from 10pm to 2am. However, they accept kids as young as 2 into their Camp Carnival. So there is give and take.