Not really. An mp3 is an upgrade from a physical CD in the fact that it is extremely convenient and portable and easily moved from one device to another. That and the fact that you can have thousands of them on a single device (which would take up a lot of physical space to have the same amount of music on CDs) and the argument that MP3s are an upgrade is quite logical.
Like everything, they have their cons, which mainly is sound-quality, but honestly, the general public has never really cared about fidelity.