K2 still delivers the same things when coupled with sigpro and allvideo.
It provides an out-of-the box integrated solution featuring rich content forms for items (think of Joomla! articles with additional fields for article images, videos, image galleries and attachments), nested-level categories, tags, comments, a system to extend the item base form with additional fields (similar to CCK for those acquainted with Drupal), a powerful plugin API to extend item, category and user forms, ACL, frontend editing, sub-templates and a lot more