I was once a power seller with over 13,000 feedbacks, but it got too hard to make any money selling. Expecially with their ever increasing fees.
I used to buy too, but not very often, I was mostly a seller.
If you have something unique, ebay can be a great place to sell it. If you want to get something cheap, it's a great place to buy, but you have to be wary of the con artists.