I don't agree about the serial port. Nobody connects to a LAN or router with those anymore. You don't even need a parallel port if you are up to date. You're gonna have a USB port, a PC Card shot, an ethernet port, and/or a built in wireless "g" to connect, and really that's all you need.
Depends on what line of business you are in. The pix firewall I have needs to first be configured by such a port - RJ45 won't help until you set up the interfaces - perhaps now they have USB but when I got it they didn't - I suspect that most companies out there won't toss a couple thousand dollar piece of equipment out just to get a usb port in it
And there are many other 'legacy' systems out there as well
/JD