I remember when Disqus Comments came out. I didn't see the point of it, as my sites already had comments and users, and it didn't make much sense to me to "lose control" of my comments. It meant that my users might need two different logins for my site, and I didn't like that.
Recently I implemented Disqus (pronounced "discuss") instead of the normal commenting system on a Drupal site, and on reading the reasoning behind using Disqus I realised why it is a good idea. With that in mind, you'll notice if you scroll down to the bottom of this page that I have changed this site's comments to use Disqus as well.
Drupal's comments work well for their use-case, and they should since the comments module has been around for years. Time marches on and technology progresses, and yet Drupal's comments have remained the same for years.
Every day there are more and more web sites and social networks, and with that people have also wanting consolidated accounts where they only need to log in to one place in order to be able to use multiple sites. While there are modules for registering with Drupal via other services, for a site like this which is just a blog, something of that nature need not be necessary. This is where Disqus steps in.
Disqus is a commenting system that integrates seamlessly with your site to provide your site with a social commenting system that can use 3rd party sites like Facebook or Twitter to log a user in. If a user does not use one of the services, they can create a Disqus account quickly and easily, which they can use to post comments on other sites that use Disqus too.
Drupal already has a module which provides Disqus integration, and it works with both Drupal 6 and 7. Simply register your site on disqus.com, then install and configure the Disqus module and Bob's your uncle!
If your site already has a bunch of comments, Disqus offers a way to import these comments. The Disqus module for Drupal comes with a submodule for exporting commets, but this submodule requires you to have registered it as an application with Disqus, and I really didn't want to do that just for a once-off import. Fortunately I found a patch to add an extra export option, which exports comments in WordPress's WXR format (though it had a small bug which I had to fix). I then went to the Disqus site and used the import tool to push those comments into Disqus. Unfortunately at this stage the import doesn't seem to work. It may be an issue with Disqus' importer, or it may be an issue with the exporter. I'm busy looking into this.
Once I had set things up on Disqus, I went and configured Drupal with the settings necessary to link the site up to Disus, and disabled the comments module. Now the old comments system is gone and the much-superior Disqus comments are active.
As you can see, it was actually really simple.