I've been using it for a few days and I still haven't been able to find the "content concentrator" or even figure out what it is.

Concentrator is well hidden butcan be found in the services menu if text in a message is highlighted.

Concentrator doesn't show up for me ... in fact, no Services are displayed when I'm using Eudora.

I can't get anything to go into the Junk mailbox either. All relevant preferences are turned on, but perhaps Junk doesn't apply to any messages that would be caught by filters. My filter set is set up in such a way that some filter will be applied to any message, so maybe Junk doesn't have room to work.

What I'd really like to see from Eudora 6.0 is the ability to control mail checks through AppleScript (i.e. check mail for specific accounts) and a MIME attachment mode that _isn't_ AppleDouble (try using Eudora to send attachments to PC users and listen for the screams as they struggle to make sense of the 'applefile' segments that Eudora insists on including). But it looks as if this is another marketing-driven release, so I'm not optimistic. I suppose we should be thankful that the new features are more useful than the little red peppers we got last time.

I'm confused as to what the other posters think the Concentrator is... I noticed that a recent long thread had quotes removed with the text "...snip..." when viewed in the preview pane in Eudora, and that when selecting multiple messages, the preview pane gave a 'conversational' view of it (completely removing all redundant quoted material) - I think this is actually quite nice...

But I haven't used Eudora for a long time, so perhaps this is an old feature and not actually what they meant by Concentrator?

Re: Concentrator, Michael has it right. The release notes say: ""Content Concentrator now working in the preview pane."
It's not in the Services menu (that "Summarize" service is system-wide and has been around since 10.2).