I deal with dense proceduralized content where long and complicated procedures need to be broken down. So, ability to zoon in/out & order matters the most.
Content is 80% RTF & 20% HTML from web pages.
I've watched on the demo's on the DevonThink channel and have been test-driving their office version. It is powerful, performing, and stable. However, outlining is not its primary focus. Everything I can do in DT, I can easily do in MS Outlook (rtf content, indexing, search, attachments, share, etc).
I also tried OL 4 & beta 5. It appears to be focused more on outlining individual single-purpose content vs. a personal info management system. I could not get most of the web pagers to paste as notes (kept disappearing).
I'll try the other recommendations in the next few days.