The Darwin port of XFree86 uses the IOKit for device driver loading and discovery, rather than the XFree86 module loader. Because of this, the XFree86 configuration file is not used on Darwin systems. The descriptions found elsewhere of devices supported by XFree86 for other operating systems also do not apply.
XFree86 for Darwin will work with any video card that you have an IOKit driver for. If you are running Mac OS X, this typically means any card that has been shipped by Apple. If a card works for you with the Mac OS X GUI, it will work on the same machine with XFree86. If you have a pure Darwin installation, your hardware support may be somewhat limited because Apple does not include all its hardware drivers with Darwin. IOKit drivers are typically found in /System/Library/Extensions/ or /Library/Extensions/.
Multi-button and scroll wheel mouse support works well with all USB mice that I have tested. I have done no testing with serial mice.