The original notion of GUI's was that the user would see familiar things on the screen and interact with them in intuitive ways. The classic example was the desktop arrayed with your documents and a trashcan into which you could drag and drop a document. Or dynamically resizing columns, where you click and drag and see it resize as you "move" it.
The great benefit of this UI conception is that people could interact with computers intuitively, viscerally. When you manipulate objects on a real desk, or even when you drive a car, you don't have to consciously think about what you're doing. You instinctively and reflexively react. It takes little mental effort. This was the goal of GUI's. The benefit of course is then you can keep concentrating on your work, not the tools. And to the extent that GUI's adhered to the model that you see familiar things on the screen and interact with them in intuitive ways, GUI's delivered on the instinctive/reflexive use benefit.
Quickly though, GUI's became overloaded with menus, dialog boxes, tabs in compound dialog boxes, cascading menus, toolbars and toolbars and so forth. The shear number of options in a big application like Excel, Word, or Photoshop is astounding. There's easily over 200 menu items along with dozens of dialog tabs. At this point, a GUI is no longer an intuitive UI, it is simply an efficient way to present very large numbers of menus and settings options.
Rather than being instinctive and reflexive, using modern GUI's are highly cerebral exercises in figuring out to do something that you think the computer does, maybe does, or possibly does.
Visceral Excel was a project I started within the Excel group to try to bring back a more visceral experience to Excel usage.
The most important idea we developed was a web UI, where the UI itself was treated as a large web of information. I built a prototype web UI for Excel, encompassing all of Excel's commands and showed to a great many people with Microsoft, with a very enthusiastic reception. The idea is to apply the expressive and navigation power of the Web to application UI -- (1) linking together the UI pages and making them searchable, (2) expressive interactive graphics which illustrate options instead of terse words describing them, and (3) bringing together all the forms of assistance that are available to the user -- help, tutuorials, wizards, templates, and examples -- in a uniform linked way integrated with the main menu/dialog UI. After all, the UI for large applications like Photoshop and Excel are quite large information spaces in their own right. I kept a traditional menu structure as convenient entry points into the UI web, but grouped the menu items by functional area along with a top-level page in each area offering introduction and an overview of the functional options in the area. I thought then, and still think, that this would be a hugely beneficial evolution to application UI. But unfortunately we weren't permitted to go ahead and implement it. The prototype is still very cool, but I assume it's Microsoft property, so I can't post it.
A second offshoot of the Visceral Excel project was the scroll wheel on the mouse. This came from watching users navigate large documents and imagining how we could make that a more intuitive/reflexive experience.
Other features included sound feedback and animations, neither of which turned out to be as useful as I'd hoped.