Rack-pjax is middleware that lets you serve 'chrome-less' pages in respond to pjax-requests.
It does this by stripping the generated body; only the title and inner-html of the pjax-container are sent to the client.
While this won't save you any time rendering the page, it gives you more flexibility where and how to define the pjax-container. Ryan Bates featured rack-pjax on Railscasts and explains how this gem compares to pjax_rails.
Check out the Railscasts' notes how to integrate rack-pjax in your Rails 3.1 application.
You can find the source from the screencast over here.
The more generic installation comes down to:
I. Add the gem to your Gemfile
# Gemfile gem "rack-pjax"
II. Include rack-pjax as middleware to your application(-stack)
# config.ru require ::File.expand_path('../config/environment', __FILE__) use :: run RackApp::Application
III. Install jquery-pjax. Make sure to add the 'data-pjax-container'-attribute to the container.
(For more see the docs of jquery-pjax.)
IV. Fire up your pushState-enabled browser and enjoy!