Like many people, I have both a desktop and a laptop. The desktop has a considerably larger hard drive and occasionally I need to access a file that’s not on my laptop. I usually do this by remotely accessing my desktop over the internet, but this means I have to keep my computer on all day, which is not necessary a good use of power.
Snow Leopard adds a new feature called Wake On Demand which, provided you’ve got an Airport Base Station or Time Capsule, wakes up your computer when needed for network access. You can set up an automatic sleep schedule so it goes back to sleep when you’re done.