I learned how to use Joomla and K2 at the same time.  I loved the added features that K2 provided, especially the ability to automatically resize pictures for different items. K2 provides over 100 options that really can help you take your Joomla design to the next level.  It has nested categories, a commenting system, social media tools, and an advanced user system.

When you set up a new category in K2, there are over 100 options. There is a way you can save yourself time by setting all of your options up for one category, and then copying these options to any additional K2 category you add.