Apple hires...

A hundred megabits is enough for a workstation. Indeed, most workstations don't even get close to the optimum throughput of their network cards, because hardly anybody takes the time to sit down and understand how fast the network can really run.

Gigabit networking is all very well - for servers - but it, too, can be broken by the use of poorly matched hardware (so the vendor of the Ethernet card chipset on the PC isn't friends with the vendor of the network switch chipset).

Whenever possible, don't leave any network card on the default Microsoft driver, and always take the cards off auto-negotiate: rationalise their speed by the job they have to do. This rule spits out a couple of side notes too. One is that all-Gigabit networks can be slower than those where the server is the only device given Gigabit speed, and the other is that network switches with more brains (generally, managed switches) tend to move data with less latency and more room for tuning, than their dumber, cheaper alternatives.

Or, if you prefer, try to spend 20% of the cost of your server on your network infrastructure. Less than 15% and the server's probably spending all its time being choked by a poor network switch.