In theory, they seem like an awesome solution. However, somebody asked Dr. Barry Eppley what he thinks of them, and his explanation of the limiting factors would explain why plastic surgeons aren't already using them and why they probably won't be viable for cosmetic surgery(augmentation).
You can read his full explanation here
http://www.eppleyplasticsurgery.com/custom-skull-implant-2tldr: The patient asks if the CT implants are useful for augmenting the lower back part of his skull, but Dr. Eppley argues that the CT-bone implants are hard yet brittle, and would require big incisions to get them in. He also says something about the edges of the implants, that the edges of them can't made soft, smooth, feathered because of how brittle the calcium is, and that this will result in a palpable step off between the implant and the skull.
I don't know. I hope Eppley is wrong, although his explanation makes sense.
Can a doctor insert a hard, foreign object into the face without leaving a massive scar? Remember the object is also brittle, so pushing it in through a tiny hole probably will break it(?).