Now that wordpress has made implementation of custom content types so much easier, it would be nice to have some smarter fields easily available to them as well. Drupal gives its developers CCK which ships with a half dozen input types and hundreds more in contrib. WordPress could emulate this behavior to some degree by providing a section in docs or another contributed area that hosted snippets for metabox implementations. Code would be mostly cut/paste with the site developer needed to change only basic metadata such as field title, description, etc. Comments could provide additional code such as validators, etc.