This is one thing that has been missing from Joomla. Awesome component.

Hint for non-English sites: Be sure that your sitename doesn't contain special characters since some blog services choke on those.

This extension will speed up your site by an enormous amount.

I give it four stars instead of five only because I could never get the JomComment plugin to work, so the cache wasn't reset when someone posted a comment. I had to deinstall PageCache on that site because of this.

On some other sites with less visitor interaction, I have it running very smoothly and it makes these sites a lot speedier. Plays nice with OpenSEF too.