However, that accessibility comes at a price. The reliance on mouse-driven self-explanatory menus has probably robbed the economy of millions of dollars worth of productive activity, because the average user now has little incentive to learn time-saving and convenient keyboard shortcuts. In this case, I think you can make the case that computers have become too easy to use. If they were a little harder, we'd be more efficient. My recommendation is that the mouse-based menus should still be there, and still tell you that ctrl-S will save your document, but should not allow you to save with the mouse. Maybe they should force the user to learn to use ctrl-S to save. In the long run, everyone would be happier. The employer saves money, the employee saves more frequently, and has less carpal tunnel syndrome.
On Mac OS X, I use a UI hack called Quicksilver. It allows me to open applications, go to URLs, and even initiate a blank email to a contact, with a few keystrokes. It's a revelation. It took me a couple of days to re-train myself to use it by default, and it's been an incredible convenience ever since. It's just a small application that starts up at boot, and it's initiated when I type a specific key combo. A little menu pops up, and when I start to type the name of the application I want to launch, the menu displays my ever-narrowing choices. When I type "SA," Quicksilver knows that I mean Safari, the OSX web browser. When I type "OSN," it brings up a small menu of OSNews-related web bookmarks, which I can select with the arrow keys. I think that this is the direction that user interfaces should move in. It's totally non-intuitive at the start (because you have to know that keyboard combo launches it. But once you know that, it's both intuitive and efficient.
The standard Mac OS X interface with its screen-hogging dock, is a perfect example of an OS being too easy to use for a power user. That's why most experienced Mac users I know have to customize their experience with Quicksilver, Tinkertool, and other hacks. I guess it's an okay work-around, but I'd like to see OS developers taking a little more interest in their best customers' needs.
Another area where operating system user interface design could use a little more innovation is in the area of information accessibility and organization. We now typically have tens if not hundreds of gigabytes of data on our hard drives. A typical family computer now plays the role of TV, video game console, photo album, family file cabinet, record collection, calendar, and document archive. Look at the desktop of a typical novice computer user and it's littered with a hodgepodge of vitally important personal documents, interesting but trivial files and photos, and absolutely worthless detritus accidentally downloaded from the internet. Power users tend to have years, even decades of accumulated documents that need to be archived, not to mention gigabytes of photos, mp3s, and videos. All the OS makers have made some steps toward aiding the user in organizing and archiving all of this data, with tidbits of true inspiration contained in each approach. However, we're far from a truly workable solution.