I have never run at Disney or done the ChEar packages. However I will be running in 2014 and my Dad will be there to cheer me on.
The main advantage of the Platinum ChEar package that I can see is access to the Race Retreat during and after the race for the spectator. I have bought Race Retreat, as a runner, so it would be nice for my Dad to also have access after the race, otherwise he'll be standing outside while I'm inside.
Other than Race Retreat access, I think there would be plenty of places to watch runners without paying for a ChEar package.