Our Disney trip was SO much fun! We are going again in March for my Birthday and In Christmas '09. Diapers in Disney are very easy to do. As long as you have a bag with baby's diapers and powder in it. I recommend putting everything in plastic bags in the bag with everything else, that way in case you get wet on a ride. My baby used about 4 diapers a day, so be sure to have a bag big enough to pack LOTS of diapers in it. The hardest part was that baby had to change his self. And that sometimes, the bathroom would be occupied and he would have to wait outside the bathroom holding his diaper bag. But like he said, the "companion" bathrooms, are just about everywhere. We only found two bathrooms, that only had regular bathrooms, not a companion bathroom AND regular bathrooms.
I definitely recommend diapers at Disney. But if you plan on being diapered there, then baby should practice changing her/him self first.
Anyone want to join us in Disney at end of March?? It would be TONS of fun!!