Yes, this has been discussed many, many times. Some people hate this style of thread representation with a passion, and some people, like me, find it to be exactly what they need to trace complex discussions.
Thanks for your input on the issue.
added in edit
PS: Sorry, forgot to mention ... if you don't like this presentation, click on any node and you are taken directly to the discussion in Twitter's interface.
If you could randomly animate the boxes on the page this could be the "interpretive dance" representation of a conversation.