BAD: Upgrade woes
As Apple controls its hardware platforms, which increase in variance from model to model, and so does the job of regression testing model compatibility with new OS versions. Although Mavericks is said to run on the same hardware as OS X Mountain Lion, its installation routine seems to have rendered a solid number of stunning reported wipeouts, although we did not experience this ourselves, in our admittedly small upgrade regimen. We found it strange, however, that Mavericks would attempt its 5GB installation payload routine without checking the sanity state of the existing file system. We believe this may account for a large percentage of reported installation failures. Mavericks is now in its second patch release, and this maturity may also help you avoid upgrade catastrophes.