I need this feature too!

It would be great to have the full flexibility of CCK (with content_profile) for user's addresses. (Or alternatively, the basic Drupal profile fields.) The address(es) could be either a flexifield (for multiple addresses), or a field group (if you don't need multiple addresses), or a custom CCK field type.

Think of sites that already have user accounts with addresses, and only now get a shop feature. They already have views and whatever other things configured for CCK fields, and the developers don't want to switch to an ubercart-specific storage for the addresses.

Obviously it is not trivial how to translate between custom CCK address field and ubercart address system. It needs some site-specific PHP, but ubercart can make it easier with two hooks:

- One hook where modules can add address proposals for the address dropdown on checkout. This would be implemented by site-specific code to return information from the flexifield or whatever. Could also be done with hook_form_alter.

- Another hook where modules can do something when an order is placed. This could be implemented in a site-specific module, to automatically update the flexifield or whatever the site uses for storing profile addresses.

I would not be surprised if you tell me that these hooks already exist.. I just didn't look (ubercart code is big!!).