Commerce Kickstart 2.x is the most popular Drupal 7 distribution ever created. Initially created as a tool to help developers test Drupal Commerce patches faster (in the distribution's 1.x branch), it was completely reimagined as a tool to help merchants and agencies evaluate the project. It features a full online shopping experience out of the box with integrations into many of the third party services merchants use to run their stores on Drupal Commerce today.
While we used to maintain a standalone, "always on" demo site for the distribution, we recently changed our approach to depend on the Drupal community tool SimplyTest for demos. Not only does it give each evaluator the opportunity to interact with the store without worrying about interference from other evaluators, but it also gives you immediate administrator access so you can log in and play around with the application itself.
To test it today, go to the Kickstart 2.x installer on SimplyTest.me, click the "Launch sandbox" button, and wait for your demo site to be created. You will be able to log in as the Drupal super user with the username / password both set to admin.