I have been using Word 2007 since it was in beta and really like all the new features. As someone who typically writes technical papers, the new features that have had the biggest impact on me are the table of contents and citation/bibliography generation tools. They are seamlessly integrated with the interface and save a great deal of time over doing things the manual way.
I use the ISO 690 numerical style for citations and am used to the standard notation of using brackets to enclose numerical references to the bibliography. The one thing I have not liked about Word 2007 since the beginning was that it uses parenthesis instead of brackets. I am not sure what the official standard is, but all of the scientific publications I read always use brackets.
For some time now I knew that there had to be a simple way to change this, and that it must be related to the ISO690Nmerical.xsl XSLT stylesheet located in the office 12 program files directory. I am a confident XSLT developer, but I did not want to take the time to go through the 7000+ line stylesheet. Fortunately, the forums at Channel 9 contain a thread regarding this very issue and someone was kind enough to list the line numbers that need to be changed.
Here is a link to the channel 9 forum post describing the changes required:
http://channel9.msdn.com/ShowPost.aspx?PostID=245923
I have uploaded a version of the stylesheet that already has the changes made. It may be downloaded here. I have also uploaded the original version in case you need to go back. Save it to your \Program Files\Microsoft Office\Office12\Bibliography\Style directory and you are ready to rock and roll. If you are using Vista, then you may have to delete the old version first and then copy the new one in to have the changes take effect. This has to do with the file system protection in Vista.
I hope this helps. Feel free to leave comments if you have any questions.