What's new in WriterMost of the changes to LibreOffice Writer -- the word processor and flagship of the suite -- have been minor, but a few of them stand out as being exceptionally useful. In previous editions of the suite, comments could only be inserted at a specific point in a document. Now comments can be attached to a range of text, such as a whole sentence or paragraph. This makes comments far less ambiguous, since you can now see the entire context of what a comment refers to. As a corollary to this, DOCX files that have commented text ranges retain those when imported.
The handling of imported DOC and DOCX files in general has also been slightly improved, which we've come to expect with each rev of LibreOffice. For instance, as of version 3.6, documents that had contextual spacing enabled for autonumbered lines now render properly, and documents with floating tables now import correctly. I have documents that exhibited exactly these issues, so it's good to see them fixed. Tablet PC users might also be happy to know that (as of version 3.6) ink annotations in DOCX and RTF documents created on a tablet PC can be imported, and native RTF math expressions can be imported and exported.
A new 4.0 feature is the ability to set variant first-page headers and footers for a given page style (what Word implements as document sections). Only ODF documents support this feature right now, but there are plans to expand support to imported DOC and DOCX files.
Most big organizations use some variety of content management system, typically one that adheres to the CMIS standard. Writer (and LibreOffice generally) can talk to such servers -- such as Alfresco or SharePoint -- to open and save documents they store.
Another CMS-related addition, by way of a plug-in, is the ability to publish documents as articles on MediaWiki servers. Writer is able to convert the document to MediaWiki markup automatically, which is genuinely handy, but unfortunately this is a one-way street: You can't point to an existing article on a wiki somewhere, import it for editing, then reexport it. Likewise, although it's possible to export a document as a MediaWiki text file, it's not possible to import it and edit it as a native LibreOffice document. Maybe the next point revision could allow this -- I suspect Wikipedians everywhere would be thrilled.
Annotations in LibreOffice 4.0 can span whole ranges of text, so it's unambiguous what they refer to. Word documents (DOCX) with such annotations now import correctly.