There are two commercial programs that you could use to sync your X3 with a Mac.
Missing Sync from Mark/Space
http://www.markspace.com/missingsync_windowsmobile.php
and
PocketMac
http://www.pocketmac.com/
I have used both programs and have had better results with Missing Sync. PocketMac would create bogus calendar entries in iCal and would also create duplicate entries. Thus far, I have not had that problem with Missing Sync. PocketMac was able to mount my PocketPC (at the time an X30) to allow me to copy files to or from the PocketPC. This feature does not seem to be working at this time for me (using an X51v with Windows Mobile 5, I have not tried Missing Sync with Windows Mobile 2003).
Right now (11/6/06), PocketMac does not work with Windows Mobile 5, but that should not be a concern for you (unless you upgrade to a new model). They indicate that support should be "coming soon."
Not being able to mount my PocketPC like a hard drive is an inconvenience, but not a real problem for me. I use VirtualPC and ActiveSync to install programs (I found both PocketMac and Missing Sync lacking in this area), and can also use that combination to copy files. If you don't have a PC (or VirtualPC), then the ability to copy files from the Mac may be more important. I do not know if this feature works with the X3 in Missing Sync, but it should with PocketMac.
Neither solution is ideal, but probably both are adequate.