If you're buying the CDR-W for the Rev. B. iMac, it's not going to benefit you to buy a faster drive, due to the slower connection. If you buy a new Mac later, unless it's a low-end iBook, or TiBook, it's going to have a burner built in, and even if it doesn't, it will have FireWire on it. I would buy a USB 1.1 spec burner for less money and leave it at that.