If you routinely copy files (especially large ones like mp3s, etc.) between machines in your LAN, then the switch will make a difference - especially when run at full duplex as this model claims it can do!
Since I have a pproxy running on my dual Xeon with 2K AS and the ppstats program on my alpha and Red Hat 6.2, with the ppstats running once an hour, I have that constant communication going 24/7 between the two. Having a switch (a 3Com Superstack II managed one), has helped in isolating their conversations so they happen only between themselves, without having that interfere with the rest of the machines.
[EDIT: Just be aware that sometimes those auto-sense things don't always work...

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