I haven't done the tubing, but I can safely say that the Falls are incredible! I'm not too fond of the merchants heading to and leaving the falls, though. They can be VERY demanding!
There are lockers where you can lock up your stuff before you do the falls. Taking a camera is ok, but video is a no go. YOu need both of your hands. A small fanny pack for a waterproof disposable is your best bet.
Also, don't forget the water shoes! They recommend these over old gym shoes, and I agree. All in all, though, it is an exhilerating experience, one that I've done twice and look to do it again soon. As soon as you're done, you'll want to do it again!
BTW - if you port in Ocho Rios, there is a place right outside the gate, to the left, called "Jerk Taj." The BEST jerk chicken in the free world. The place doesn't look like much, but it is outstanding food.
