On my last trip, I did all four parks on my last day.
I already knew what I wanted to hit one last time or catch before I left, so I kinda had a plan of action in my head.
I also had broken my toe the night before on the bed post, and after hobbling my way around DAK in the first part of the morning, my friends insisted on getting me a wheelchair as opposed to watching the painful grimace on my face for one more minute.
We used Disney buses and the monorail. We even went off property for lunch and to pick up my prescription of pain killers from the local Walgreens.
I found it very doable, and it was in the middle of August, one of the busiest times of the year for Disney. So in my opinion, park hoppers are well worth their cost.