I use Lotus Notes every day. The UI has made some big improvements, but it's still counter-intuitive.

>I seem to recall working for a company that used it for exactly that. All documents related to a given project were hosted in Notes, and could be updated by anyone. This was in the mid 1990s and things have probably changed.
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>I am not speaking as a fan. Some of the UI was so counter intuitive you wondered if they were just having fun with us. There was a document at the time about bad user interfaces. Notes had its own section.