Gamin is a Gnome project that reimplements the FAM specification with inotify. It is newer and more actively maintained than FAM.
To replace FAM with Gamin simply remove the FAM pacakage, ignoring dependencies, and install Gamin.
pacman -Rd fam pacman -S gamin
Remove fam from your DAEMONS line in rc.conf if it exists. Gamin does not use a daemon.