I had a friend who used to work on the team that runs Pal Mickey at WDW. They stated that it was originally planned for DL, but it's success rate at WDW was not large enought to justify the set up costs for DL - which were very expensive. Not sure if the demographic here would support it.
We thought Pal Mickey was worth the purchase price (in fact, we actually have two), but we really used it to the max. We got them before we had kids and just found the fun in where and when he "went off". We made it sort of a treasure hunt for his transmitters.
Just a note on how they work. The character sightings and attraction update transmissions are actually manually sent to the Mickeys. The parade one is really the only one of those that is on a schedule. A Lead CM (who is on the Mickey team and works in their own daily position, as well) controls the manual transmissions. If there is no one manning that position, then they won't be sent out.
Nancy