The hike was fine. Stupid sore afterward (wasn't prepared enough for that one). This was done in a day (I think it was 13 hours).
The funny thing about doing it that first time was I discovered in my backpack that I carried some textbooks from school across the grand canyon. Made this discovery as we unpacked at the end.
My other rim-to-rim hikes were fine. Had to help out some family members and friends with their issues though (it does get stupid hot down there).