Just for anyone else who stumbles on this thread...

I've recently the formfilter module and it seems to work quite well. It allows you to hide form elements for every form through the UI, instead of creating a module just to use hook_form_alter. Since each product class is a different node type, each will have it's own form which can be controlled by formfilter. Not what you need if your doing any heavy modifications to forms, but great for just hiding a few fields.

http://drupal.org/project/formfilter