Building off of DamZ's work, I've been expanding product support over the last couple of days. To test it out, grab the latest code from http://github.com/rszrama/drupalcommerce and Drupal 7. I'd recommend using the installation profile I posted about to start up a fresh Drupal Commerce dev site. Once you're in, you should see the Commerce menu on the Admin Menu, or you can browse to /admin/commerce/products.

As of right now, you can define product types / add fields to them and then go create products. The main product view is in fact a View, and we have full Views support for the base product fields, including handy little edit / delete links. There's still a little bit of work to be done on the basic APIs here, including functions to instantiate new products / types and calls to drupal_alter(), but I'm happy with the pace of development so far. I'm going to try real quick to get a product reference field started, but I need to hit the sack soon.

If you have a moment, you might check it out, report any bugs, and point out holes in the code thus far. What sort of things will you need to do with a product API? What functions seem to be missing? What documentation seems to be weak?