One of the best parts of running a blog is interacting with your readers via the comments they leave. Unfortunately the default Blogger commenting system is very basic and does not provide many features that other systems have. I migrated all my blogs over to Disqus and our users love it. We're getting around 5*times the number of comments than we did before and Spam comments is almost non-existent. It's very easy to install into blogger, has great Spam and Moderation options to ban spammers and IP addresses and allows for threaded conversations. It allows people to log in via Twitter, Facebook, Google, or just email/Username or Anonymous.. you choose. A lot of the large blogs/sites around the internet are using Disqus to power their discussions. It fully imports your existing comments as well as keeping them in sync should you ever want to remove Disqus. And best of all it's totally free :) You can see it in action on my blog here http://www.spoilertv.com/2010/1