Yep, I like Disqus it is a really good commenting tool for blogs. Also, if you use gravatar there is a way to make all your disqus posts appear with your gravatar avatar!
It also works nicely with twitter and facebook.
It is very clean, but it is for commenting on a single topic with various different threads.You can see how the replies indent and break up the different "threads" of conversation - I think implementing a similar "reply" system would make some feel they're being ignored, or equally, obliged to give everyone the same amount of attention.
I think being able to reference one another might be a good idea, for example with the twitter-standard @username. What do you think it is that makes it so "clean"?
All the best,
Spare Ed