1. Extra-fields gives you perfect control over your content.
2. Control over how the content boxes be displayed.
3. Multiple level of categories.
However, 2 things desperately needed by are missing in K2 are:
1. X-Map extension
2. Advanced search module, which which user can search all the fields, SPECIALLY the extra fields added.
Thanks for FREE distribution of such a great extension!
1. Actually an Xmap plugin for K2 already exists. Google it and you'll find 2 of them ;)
2. K2 offers integration with Joomla!'s search (show K2 itesm show up on your "site wide" search) plus it offers a module to only search K2 content. It's on our plans to create a more sophisticated search engine view for K2, fully configurable. And it's coming soon! :)
Thank you for your kind words!