Over the years, I've watched a lot of people use PowerPoint. And I think I can safely say that a lot of presentations would take a lot less time if people entered their text using Outline View, rather than typing it directly into the slide. PowerPoint 97 had separate Outline and Slide views, so switching back and forth was kind of a pain. But now with PowerPoint 2000 (and later) in the standard Normal view, you can see the outline right next to your slides in a separate window "pane."
Adding text is a big part of creating any presentation. Generally to edit text in Slide view (or the Slide pane of Normal view), you click the sample text in a placeholder. The arrow cursor changes to an I-beam, which indicates you can start typing. This approach works okay if you are one of those people who prefers to type and format your text at the same time.
However, most people type first and format later, since it's hard to compose text if you are busy thinking about whether a word should be bold or not. So it's often easier to just blast out your presentation text first and not worry about the formatting until later
This situation is when entering text in Outline View (or the Outline pane of Normal view) can save you a lot of time. In the outline, you press the Enter key to add a new Slide title. Then you press Tab to demote an item, such as turning a slide title into a bullet point. You press Shift+Tab to promote an item, such as a turning a bullet point to a slide title. Pressing the Enter key lets you continue typing text at the current level. For example, if you are typing a bullet and press Enter, you can type another bullet. It sounds confusing, but it's one of those things that makes sense when you try it out. Using just three keyboard commands, you can add text really quickly with absolutely no mousing around.
After you've input your text, it's easy to reorganize it in your outline later. Click the slide icon to the left of a slide heading and all the slide text is highlighted. Then you just click and drag the slide icon and text up or down the outline to a new location in your presentation.