The installer for XTools 1.0.2 erased my Applications folder, /etc, /usr, and root home directories, and much more! Other users had experienced such problems with earlier versions, and Tenon promised to re-release the application only after resolving the issue. I installed on Mac OS X 10.0.1 over XTools beta10 when Mac OS X started to fail during the system optimization step.
The Tenon XTools discussion board at www.tenon.com has more information about similar problems suffered previously by other users.
[Editor's note: Please see the comments for a response from Tenon; the install issue is particular to those who installed OS X over the PB and then upgraded to 10.0.1; thanks for the clarification, Tenon!]
Mac OS X Hints