Live View on a 7D is most useful when the camera is relatively static rather than for fast-moving subjects.

Good uses include:

• tripod work such as landscape, architecture, and cityscape
• manual focusing, especially with manual-focus lenses
• checking critical focus using the magnified view
• reducing vibration, since the mirror is already up in Live View
• previewing exposure with exposure simulation
• situations where contrast-detect AF or face detection may help

Why it helps: the 7D’s optical focusing screen is optimized for autofocus, so precise manual focus through the viewfinder is less ideal. In Live View, magnification makes fine focus much easier. It can also improve sharpness on tripod shots because mirror movement is minimized.

It is usually less useful for sports, portraits, or other situations where you or the subject are moving a lot, because the optical viewfinder is generally quicker and easier to use for action.

So even without an articulating screen, Live View is still very useful for careful, deliberate shooting—especially tripod-based and manual-focus work.