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.
Plugin works also in Joomla 1.7.5
Feel free to ask questions in comments on extension's download page.
All I had to do was install, set the module to a position and pages and then get a Disqus API key for my site.
Otherwise, it style looks great without any effort.
The level of difficulty here is very low and I'm a relatively new user when it comes to Joomla! Thanks so much for this great tool!