I like mid ship (not as much rocking from the waters). I have been on a 3, 4 and 7 day cruise in a Cat. 11 with our family of 4 (DH, me and our twin daughters who are now 10).
I like being on the 6th floor because it is one floor down to the Kids Lab and then just 3 up to the pool (those are our two main areas that we go to for the kids).
The rooms are nice. There is a curtain that you can pull between the bed and the rest of the room for privacy. That was great for 'getting dressed' (my girls like going into the 'bedroom' to get dressed. During the day the bunk beds are put away and you have a couch and coffee table. At night the kids have bund beds and they can see the TV from them.
We did not spend a lot of time in our room, but we found it to be fine. Our 4th cruise that we just completed last week was in a Cat. 10 with a secret porthole room. We did really enjoy the natural light and the split bath. But I wouldn't hestitate a minute to go back to a Cat. 11 if I had the chance to go on another cruise. Most of the Cat. 10s are on the 2nd floor, and I don't like being that low on the ship, so if I can't get a SPH, we will probably go back to a Cat. 11 room again for our 2005 cruise.
If this is your first time on the ship, you will find EVERYTHING magical and wonderful. We like to do new things each time we sail, so this time one of our 'new things' was trying a different type of room. But bottom line, the Cat. 11's are just fine. In fact they are beautiful and you will have a great trip and enjoy your room VERY much.
DJ