I have not done it but it sounds like so much fun!! and not gruelling at all. They do have a time requirement but I'm not too sure that it's actually followed b/c I saw the times for people last year and there were definitely some people over the specified time. I can't completely remember what it was just now - 16 min mile maybe???
Basically there aer 3 parts to the challenge...
1- 5K Race through Animal Kingdom parking lot - into and through the park and back out to the parking lot
2 - obstacles - quite simple such as jump hay bales, run in tires, balance beam and a net to climb (I do believe the obstacles are NOT mandatory and you can go around them but as I've never actually been do not hold me to this)
3 - scavenger hunt through the animal kingdom park.
I think it's been done two ways -
run with obstacles spread out throughout the run and scavenger hunt after that is done
&
run, then obstacles at the end, then scavenger hunt.
Not completely sure HOW they plan to do it this time but there is talk of looking for clues while you run that will help you to solve the clues at the end and I'm not sure if the obstacles will be through the course or after.
Hope this helps

Oh - it is an evening race and will start I beleive at 9:30pm this year. There is a party in the park afterwards and DinoLand will be open (with Dinosaur) as well as Expedition Everest and Kali River Rapids. You get the after party pass with your registration and if you want non running family members to join you for the party you will be required to buy a party ticket for them. Regular park tickets will not get you in.