About Page Slide

Usage

To reveal additional navigation controls
In TV or mobile space since controls and/or space is limited
To expose a configuration panel (similar to the Module Configure Pattern)
To a lesser extent to reveal help or contextual information (the partial hiding of the related content might make it a poor choice for this)

Challenges

Discoverability
Losing context with the rest of the page
Make the disruption work for you

Recommendations

Use it sparingly only for major context switches
Make the animation fast. No reason to wow the user with your ability to scroll
Make the activation/deactivation dead simple

For more information visit Designing Web Interfaces: Page Slide