Kristen and I have been looking to purchase a good used piano for some time now. I've kept my eye out for good deals on both craigslist and Ebay. Several weeks ago we found a very very nice one on Ebay, which we bid on and won, but the seller backed out. We were disappointed. This week we found yet another, but bid unsuccessfully as the reserve price was not met; however, after the auction I contacted the seller and she agreed to sell her piano for a few hundred dollars.
Yesterday we went to pick up the piano and were pleasantly surprised by the piano's condition. It's almost thirty years old, but is in beautiful condition (besides needing a good tuning). We wrestled the piano out of the seller's house, into a truck, and into our living room. We are looking forward to having a piano over the holidays.
Generally speaking, I would recommend buying a piano on Ebay. Because most people are very wary about bidding on a piano sight unseen over the Internet, and also are generally unwilling to pay the large shipping costs, often pianos sell for much less than their fair market value. I would recommend waiting for a piano to come up in your area. Then you avoid the shipping costs and can actually go look at it before you complete the purchase.