I've mentioned that Microsoft Word has its faults, but one place it is ahead of OpenOffice is in document comments. The issue in particular is that MS Word allows you to apply a comment to a region of text, whereas OpenOffice only allows you to insert a comment at a particular position in the text.
It's important to know which region of a document, from beginning to end, a comment applies to. A comment at one point in the text doesn't give the necessary information about just how much of the text is affected.
This is really important if you are doing document reviews. Rather than adding edits directly to the text as part of the review, it often works better to add comments because they are non-destructive, and the document editor can then take a global approach to implementing the comments once they have been decided. Comments often end up being interlinked, they can't just be implemented completely independently.
For this, which happens a lot when working on standards (for example), MS Word is just easier to use. That's frustrating for me since I otherwise prefer to use OpenOffice. However, the next version of the OpenDocument file format, version 1.2, is supposed to support full round-tripping with the Microsoft Office file format, and so I'm hopeful that future versions of OpenOffice will support a better approach to document comments than they do now.
Fingers crossed.