Network booting via PXE can be a life-saver when you have a box that won't boot by any other means, or you want to roll out upgrades across a hundred machines without jamming a CD into them individually. Our PC Plus brethren have put up a tutorial for booting Linux via a network connection, explaining how to install a DNS server, configure DHCP and set up TFTP to transfer the boot image.
Two years ago, the small business where I work would never have considered selling Linux systems. When it comes to computers, the vast majority of our customers are only familiar with Windows. Trying to sell them an Ubuntu system would have been similar to what Sisyphus experiences with his boulder.
Times have changed, however, and now it's a bit easier - especially since I can demo a system and show that they'll be able to do many of the same things even with a different OS powering the computer.