Plone works well for managing the publishing process and storing research notes, and has the advantages of overall document organization, workflow, single sign-on for multiple documents, etc. However, it is not ideal as a system for high-velocity collaborative document editing.  For details, see the section below.

In the past few months, several web-based document editing services have appeared.  These are free, require no downloads since they run entirely in the web browser, are password protected, and offer critical change-notication features.  Two of these services are profiled here.

As long as tools like these remain free, both in terms of cost and the ability to export/extract data, they seem like the optimum solutions for dynamic documents. Once the documents are stable, they can be placed within the Plone site for comment and future reference.

Note: Because these are free services that are provided without any comprehensive security features such as encryption-in-transit, they should not be used for any particularly sensitive information.  There is also the risk of service disruptions (make backups) and the risk that the companies might start to charge a fee for even the basic features.

Writely

Writely is a collaborative document editor with real WYSIWYG editing and RSS feeds for revisions.  A document can be created directly within the system, or you can upload a Microsoft Word or Open Office document.  According to their FAQ, they support the Open Document Format:

We support direct conversion from and to ODF.

You can also manage several documents within the same context, and 're-use' collaborator accounts.  The revision browser will highlight changes, color-coded by author. The RSS feed for revisions is a little awkward, since it uses GMT + timezone offsets to display the edit time (e.g. "Fri, 20 Jan 2006 05:05:42 -0800"), but it's better than nothing.  It might be interesting to have these feeds appear in a Plone portlet as a way of bridging the two systems.

Update: Writely announced they were acquired by Google on March 9, 2006.  This is probably a positive for long-term stability, but they aren't taking any new registrations until the transfer is complete.

WriteBoard

From 37 Signals, WriteBoard is a free version of the editing system that is used within BackPack.  WriteBoards are okay for plain text, but require special codes *like* _this_ to be added if any formatting is desired. It also lacks the input/output features that Writely has, and only offers export in XML.  Using it within a paid account in BackPack could provide a level of organization above the individual document level, but overall, Writely seems like the better choice.

Why Not Plone?

• No native handling of editing contentions.  Two people working on a document can over write each other's changes.  The normal solution is to have a check-in/check-out system to lock a document into read-only mode for everyone but the person currently editing it, or at least have some visual cue that someone else is editing the document.  This is not built in to Plone, and the Locking Workflow product has not been reliable.  One user could call or email every other possible editor of the item to notify them it is in use, but this is obviously not practical for users spread over distant geographies and timezones, and defeats the purpose of having an online system.
  
• Comment synchronization.  Comments are only relevant to the original version of the page or file.  As the document continues to change, the old comments no longer make sense, and the process becomes very confusing.  The solution is to do a "Save as..."-style trick: make a copy of the page, put the date or some sort of revision code in the title or description, and then add new comments to the new document.  This puts the burden on all users to know and follow a multi-step process, rather than having it happen automatically.
  
• No inline comment ability.  Comments must always be added to the bottom, which requires a lot of scrolling if comparing multiple versions.  The comment text box is also quite small, though that could probably be fixed by editing a skin.
• If editors make their changes directly to the document there is no way to tell who added what.
• No end-user friendly versioning or rollback, and hence no rss on changes.
• No easy way to see who has access to a document. Since we have configured access via groups you would have to go to the Groups tabbed while logged in as a manager to see the list of people who have access to edit the document.  This makes it harder to send an email to your co-editors to notify them of changes.
  

Why not Wikis?

• Most use non-intuitive editing codes for formatting and links.
  
• Intimidatingly unstructured for non-geeks.
• Unless each editor is careful to add their name to each addition/comment, it is hard to follow the evolution of the document as a sort of 'conversation'.