Quite a while back I won another error pony on ebay. I got it in the mail and put it.... somewhere before I could take photos. Just a few days ago I happened to find it (of all the places sitting on a shelf will all of the other ponies).
This Cheerilee is not terribly different from her standard counterpart with the exception that she is factory sealed with a blue tail.
I also noticed that her purple plastic color was significantly different from the Cheerilee set that comes with the Cutie Mark Crusaders.