You've been thinking about Gigabit Ethernet for a long time now, haven't you? Perhaps you've even installed some server-to-server gigabit network links, although price tags of over a grand per port have likely kept you from deploying it to the desktop. That was then, this is now.
Today, you can get gigabit switches at prices that drop the single port cost to less than $100. At that price, you can afford gigabit not just on the server farm, but all the way to bandwidth-hungry users as well.
Of course, you don't want to drop gigabit to everyone in the company. While the price per port may be affordable, there are other factors to consider. First, you may need to replace your cable. If you upgraded your wiring plant recently, you may already have Cat 5, the minimum for gigabit, installed. On the other hand, if you last touched your cables in the mid-'90s, you probably still have Cat 3. In theory, Cat 3 is only capable of supporting for 10Mbps Ethernet, although in practice, people have often forced 100Mbps Fast Ethernet to run over it -- well, sort of run over it. Ideally, you'll want to use Cat 5e or Cat 6 cabling, since Cat 5 really is a minimum (the same way that 128MBs of RAM is a minimum for Windows XP Professional).
Additionally, the vast majority of PCs aren't fast enough to deal with gigabit Ethernet. A run of the mill cheap bus in a computer only runs at 133MBs per second, which is nowhere near fast enough to take advantage of gigabit's speed. Newer computers using faster buses with 800MHz speeds, such as those based on Intel's 875P chipset (aka Canterwood), can, in the current generation, deliver peak bandwidth in the 4.2GB range. That's more than fast enough to deal with gigabit Ethernet. In your servers, you may already have PCI Express (PCI-X), once known as "Third Generation I/O" (3GIO), buses. These can handle one GBps, so they're more than up to the gigabit Ethernet challenge as well.
Still, the bottom line is that you're almost certainly going to need your upgrade your client PCs if you really want to enjoy gigabit's speed benefits. If you can't, while gigabit Ethernet will deliver a performance boost of about 30% over Fast Ethernet on standard Pentium III and higher computers, it's not really cost effective since Fast Ethernet ports cost only a third of gigabit Ethernet's ports. While gigabit's much cheaper than it used to be, so is Fast Ethernet.
You should also be wary of computers that come with combination 10/100/1000 network interface cards (NICs). Just because the PC has a gigabit NIC under the hood doesn't mean the bus will actually fully support that speed. Buyer beware: if you buy PCs to use gigabit Ethernet, make sure the bus is PCI-X, 875P, or another high speed design. Just like computers with integrated graphics sound like a good deal, users who need top performance will ultimately find them disappointing.