Just installed the Disqus commenting system on my Tumblog. Took me 5 minutes. Great. Nice thing about Disqus is that it lets you login with your Twitter account for example and aggregates discussion elsewhere on the Web about something I posted. And why a commenting system at all? Like they say themselves:
“Why do people write more comments on sites using Disqus? It’s because we believe that there’s no difference between a great comment and a great blog post.”
Fire away!