In the past I've used this to launch directly into Steam. My friend has a spare PC in his living room mean for games with an open invitation for anyone to use, but didn't like people abusing it/his internet (We have data quota here, iirc his is 75GB a month then he gets throttled to 65Kb/s), so he asked if I could make it for steam games only. Now when you turn it on, you get a steam login prompt, and basically nothing else. All the installed games are available to anyone who owns them on steam, and work normally.
Hitting Ctrl+Alt+Del, opening the task manager, hitting File->New Task and running explorer.exe gets you the start bar back, so its not locked in or anything.
In general its pretty useful if you have a Windows box that's used for basically one thing, like XBMC or Steam.