I don't normally review extensions, but I was amazed at this one. I wasn't sure at first why it wasn't showing up straight away. Read the documentation which explains *everything!* and set it up following the steps and it dropped in perfectly with no fuss. Even the styles don't need changing. The default is so simple and clean that it should match pretty much any website. This was so perfect, whereas the module I used for the 1.0 version of joomla needed a lot of css work to make it appear seamless. I am extremely happy with this extension!
My only suggestion is to have the email address as an optional instead of a required field incase guest commenters want to be notified of more comments - ie in my case they may ask a question about an article and people can answer it, but at the moment they won't know unless they come back to the site.