All three modules provided by Commerce Extra aim to improve the Drupal Commerce experience with some small tweaks. The module is in development status and some other submodules may be included in the next future.
The first submodule is Commerce Extra Address Populate, it uses an addressfield added to the user account for pre-populating any customer profile address information in the checkout phase.
Commerce Extra Login Page adds an extra step in the checkout that exposes a login form that is displayed only if the user is not logged in.
Finally, Commerce Extra Quantity enhances the look and feel of the quantity widget wherever it is, both in the cart view and the add to cart form.