For you. For me. Not for grandpa. And there are more grandpas than hackers right now.
Immediate visibility of functionality, dropping the filesystem metaphor, standardizing and simplifying the installation of software, and enforcing a consistent UX works better than WIMP for a significant portion of people who would rather not expend effort on making their tools carry out their will. (Only, of course, if their wills are relatively simple. But the intuitiveness vs. power tradeoff is a technology problem, and one there is going to be market pressure to solve.)
This sounds like a statement out of 1985. It's belied by simple facts: penetration of smartphones and tablets into the "general population" is no better than it was for web browsing and general desktop computing 10-12 years ago. It's selling more devices, mostly because they're cheaper but also because they're inherently personal. Kids that would have shared the family PC in 1998 now expect their own 4S to carry.
And that's not to say that there aren't usability enhancements in the new devices that are worthwhile. But don't pretend that smartphones are "opening computing to a whole new world", becuase they aren't. Like the desktop PC before them, they are the tools of the middle class.
Immediate visibility of functionality, dropping the filesystem metaphor, standardizing and simplifying the installation of software, and enforcing a consistent UX works better than WIMP for a significant portion of people who would rather not expend effort on making their tools carry out their will. (Only, of course, if their wills are relatively simple. But the intuitiveness vs. power tradeoff is a technology problem, and one there is going to be market pressure to solve.)