The default Mac OS X 10.4 has a default configuration for delayed ACK that made some of my network operations unbearably slow, most notably Samba. This note on Mac OS X Hints fixed things for me, improving transfer speeds noticeably. The short version: add net.inet.tcp.delayed_ack=0 to the end of /etc/sysctl.conf and reboot.
/416/improving-network-performance-on-mac-os-x - macosx - 0 Comments - 2007-06-16