As we have many many categories/items in our K2 site it was a bit of a task to create new instances of the module for each page. It also created a lot of unessential clutter/pages in the module manager for duplicates of the extension showing different lists of content.
After suggesting an auto feature that pull the category based on what page the module is being displayed on the DM team very quickly made the improvement and posted a new version for me to download! ABOVE AND BEYOND SERVICE, and a VERY USEFUL new feature.
We now have only a single module instance that automatically populates a list of items for every new category we add. EXCELLENT!
I'm very happy with the templating ability. The CSS is well written and commented and once you set up your own K2 style it's easy to get in and customize extensively.
Extra fields are a nice feature and combined with some CSS edits for the front end can make for very convenient data entry for your front end authors.
Tagging feature is also great and helps a lot for intelligent searches.
So far the ONLY really issue I have is that unlike systems such as VirtueMart, you CANNOT have the same item (product, article, etc.) in multiple categories. This is a big problem for catalog sites that want to reference the same piece of information in multiple locations for ease/method of search.
I really hope this feature can be added soon!