For years now, I've used Microsoft Office, running on Microsoft Windows. And for years, every time I've wanted to do something out of the ordinary -- something I don't do often, something I have to think about how to do -- I've spat and fumed about how Microsoft manages to hide simple functions deep inside complex menu structures. I have heard more than once that MS designs its Office menus not to make actual use easy and intuitive, but to make software demonstrations a bit more impressive. If that's true, it's not quite as bad as the story behind the QWERTY keyboard design -- intentionally created so that usage speed wouldn't overwhelm 19th-century mechanical capabilities, but it's at least somewhat close.
I got a pleasant surprise (if a small one) when I started using my new computer at work. I've used pretty much every version of MS Windows from 3.0 on, and while they sometimes got better they never got good. One of the things I disliked about Vista -- the almost-newest Windows flavor -- was that it was easy to put the computer to sleep, and harder (took more attention) to turn it off. Since one of the things I preach to employees at Greenback U is to turn their computers actually off if they're going to be away from their desks for more than about an hour, I found the sleep-mode-encouraging interface design unhelpful.
Thus, one of the first things I noticed about Windows 7 (the most recent flavor) was that the easy choice is now to turn the thing off, and it's putting it to sleep that requires extra attention. My tech people tell me that Windows 7's sleep mode is far more energy-efficient than Vista's sleep mode was (although I haven't seen numbers on that yet), but "off" is still better than "asleep", and they say that the new "off" mode also uses less electricity than the old "off" mode did. (Modern PCs, even when they're supposedly entirely off, still draw a little bit of current. The only way to stop that entirely is to cut off power upstream of the PC itself. A common way to do that is to pull the plug or switch off the power strip.)
So, specific numbers aside, the important principle here is that the software is designed to make the more sustainable behavior the easier one to do. That's a lesson a lot of product designers could take to heart. Engineer for human laziness and you'll usually get the behavior you expect.