The BBC carries an opinion-piece recommending FLOSS for business. While the piece recommends FLOSS generally, the specific example given is Drupal, a web-content management tool. The same advantages apply to all the infrastructure of IT, not just servers and networks. FLOSS is the right way to do IT and should be used on client machines as well as servers. Far too many organizations neglect web applications and support huge overheads running particular applications on PCs when they could get better performance and lower costs running GNU/Linux and FLOSS apps on the server and GNU/Linux on the thin client.
“open source delivers innovative solutions to business problems, faster and cheaper.”
I recommend Debian GNU/Linux because it has a huge repository designed to work on client or server and easily maintained whether you have one or thousands of clients.