My rsync_long_args looks like this:
rsync_long_args –eahfs –delete –numeric-ids –relative –delete-excluded

I have two issues. First, it takes a _really_ long time to do a full backup (3 hours for 60GB on a dual 1GHz G4). Second was that rsync 2.5.7 doesn’t seem to have a –link_dest flag (my build doesn’t for whatever reason). Since the OS X cp command can’t make hard links, I use gnucp instead, which does seem to preserve resource forks. I don’t recall where I got my copy of gnucp (maybe it’s included with 10.3), so you might want to test it with something like this:

$ cd /System\ Folder
$ gnucp -l Finder Finder_link
# make sure the inode is the same:
$ ls -i Finder*
430 Finder 430 Finder_link
# make sure the resource forks are the same:
$ /Developer/Tools/DeRez Finder > /tmp/Finder.derez
$ /Developer/Tools/DeRez Finder_link > /tmp/Finder_link.derez
$ diff /tmp/Finder.derez /tmp/Finder_link.derez