As a household we switched completely from using Windows to Linux about five years ago. I had been using Linux as a file/mail/web server for much longer, but our desktops were running Windows 2000. As a former Windows developer and network admin, I was familiar with running Windows. However, I was fed up of the complexity and amount of work involved in maintaining even our small network of five desktops. I had already tried using SuSe as a desktop, but at that time it didn't work out for us. When Ubuntu Hoary Hedgehog was released, I installed it and could immediately see that it was the right distro for us.
I installed it on all the desktops. Most of the family just wanted to read their emails, write the odd letter and browse the web. Since they were already using Firefox and Thunderbird they didn't notice much difference in the way the used the computer. I did have some problems getting things like Flash to work, but managed to sort these out. As the Ubuntu releases rolled out setting up systems became easier as more things "just worked" out of the box. Most of the children's games worked using wine, probably with less fiddling about than using Windows.
I had been using various flavours of *nix systems since 1990, so I probably had less problems than the average Windows user switching to Linux. Once we had switched to Linux system admin became much easier. All configurations were stored in text files and could be maintained using version control, no more regedit. The operating system could be stored on a separate partition from user data. Managing security was much easier, since Linux was secure by default and didn't need anything special setting up. Virus and Trojans almost completely disappeared off the radar. System backup and restore using Clonezilla was very easy.
In addition to desktop systems we now run a MythTV backend, two standalone MythTV front ends, a couple of Linksys slugs with Debian installed and a Sheevaplug. My main file server box runs Xen under Debian and has virtual servers which run mail/web and the security cameras using motion. Deploying a new virtual machine on Xen is very easy, which means that I can quickly setup a new box to test something out.