I did! I figured that it would never hurt to try, and it worked. It was a paid medical collection from a hospital bill (paid in full in June). I sent them a version of the GW letter I found here and asked them to remove it since I did pay it in full and I gave them a big sob story to explain why it was in collection.
I still haven't received a letter and haven't had any changes on Scorewatch, but I pretended like I was going to dispute something with EQ and when I got to the list of debts (with all the boxes you have to check), it wasn't there! Hopefully SW will update soon...I am SO ANXIOUS to see how much (and if) my score goes up.
Good luck!!!