After few days of searching proper comments system for this site and after long waiting for DISQUS plugin for J! 2.5 from JoomlaWorks I've decided to make my own plugin. It was not very easy for someone, who never tried creating plugins for Joomla CMS.
It is very simple plugin. Comments and comment form is triggered in K2 comments place. There is also comments counter on category page under each item and counter with link to comments in item's toolbar.
Plugin comes with two language files: polish and english.
Feel free to ask questions in comments on extension's download page.