At EasyBib, we're heavy users of composer and AWS OpsWorks. Since we recently moved a lot of our applications to a continuous deployment model, the benefits of speeding up the deployment process (~4-5 minutes) became more obvious.
He talks some about the current needs of their deployment process and how one option - symlinking the "vendors" directory just wouldn't work. Instead, they make use of Ruby and Chef to work with the OpsWorks hook system that fire on deployment. He includes the example Ruby scripts they put in place to handle "before migrate", "before symlink", "before restart" and "after restart" events. This new setup saved them about two to three minutes on their total deployment time and resulted in a much more stable environment.