No, I haven't personally been to one. But I have friends that have! They scored big too. A group of them went in together and pooled their money. They tripled their investment by selling off everything at a yard sale. It was amazing what people paid for the stuff.
I also know a couple who have an agreement with a storage facility. Whenever someone doesn't pay the rent, these folks go in and clean it out. They have a huge community yard sale about 3 x a year with all the stuff. They makes thousands of dollars.