Tools vs. Agents
New Architect's By Design: Wisdom from the Industry gives off lots of sparks, especially this one from Henry Lieberman, Agents Research Lead at MIT Media Lab:
Applications and menu operations are like hammers and screwdrivers. Each is specialized to do a particular task. There's nothing wrong with tools, but having a different tool for each task means that if you want to do too many things, you get too many tools, and it takes too many steps to do anything.
The alternative is to cast the computer in the role of an assistant or agent, like a travel agent, a secretary, or a real estate agent. Computer agents don't have to be as smart as a person, but they do have to be proactive. They do have to learn from interaction with the user, and they do have to be sensitive to context.
I think another advantage might be in the form of directly replacing tools with agents, even if the number of tasks doesn't decrease, the amount of repetitive effort will via automation. As Lieberman says, agents can be like 'macros on steriods'.