My late 2012 iMac was one of the affected units which may have a faulty hard drive. I took it in to the Apple store recently and had it replaced. One of the reasons that I took it in is because I noticed it making a lot of clicking sounds. Now that I have the computer back, I still hear a lot of clicking sounds coming from the hard drive. Is this normal? Also, I saw on another thread that they are replacing the drives with drives of same model number. I'm assuming they are refurbished drives? My replacement one reads: ST3000DM001