You can use them interchangeably here, in my opinion, but "of" is most common when speaking of a particular item, e.g., your own camera. If I were reviewing that type of camera, I might more naturally use "on."
"My opinion on [that is, concerning] the new Ipad is that it is only marginally more useful than the Kindle."
"What is my opinion of your new Ipad?" "It works great!"
But these are fine points. You could get away with any of these, at least here in the U.S. That is my opinion, in any case.