uc_file module that allows selling files in Ubercart is definitely not perfect in terms of API, but it is a nice piece of functionality.

In Drupal 7, it’s easy to show calendar (ui.datepicker) date selector to user.

In Drupal 7, the direct access to entity fields (CCK in d6) is different. In Drupal 6 you write:

Today I’ve made another decision to postpone using Commerce in our project where customer needed simple e-shop. I’ve actually made such decisions several times already, and that makes me feel unhappy.