My boys were 8 & 10 when we cruised (4-day) 11/00 and will be 9 & 11 for our June (7-day) cruise. They both had a great time and can't wait to go back.
They both enjoyed the Oceaneer's Lab, although were not there constantly. My DS10's favorite time was late at night when there were no planned activities and he could just play on the computers. I think he was one of the last to leave every night! The kid's navigator shows the planned activities in the lab for the entire cruise. We would look that over and decide what things interested the boys and plan accordingly. They tried out a fair amount of the activities, and admittedly not all were a hit, but nothing was bad enough that they didn't want to go back. I don't recall too much Disney-type stuff for the older kids the way they have for the little ones. I don't think either of them really made any specific friends, and they were in seperate age groups so were really only together late at night. That didn't see to bother them at all, but then again they've been in day care all their lives so they're used to that kind of situation.
They also got an arcade card and spent a little time in there, but I think just enough to spend the $10. We played ping pong a couple times, and they went swimming. We ate all meals together - DS8 pretty much stuck to the kids menu, but DS10 loved being able to order the fancier stuff from the regular menu.
All kids, just like all adults, are different, and I don't think there's anyway to know for sure whether your DS will really love cruising or not. I would recommend getting a copy of the kids navigator from Dave or Barb's site and looking it over with your DS. Some of the descriptions are kind of vague, but it will give a general idea of what to expect.
I have no concerns that my DSs won't have a great time on our upcoming cruise as well!
Enjoy!