This conversation on Slashdot about OpenOffice officially dropping the Aqua implementation in favor of supporting only the X11 version for Mac, led me to NeoOffice/J, a Java-based implementation of OpenOffice which does integrate well into Aqua:

NeoOffice/J is a fully-featured set of office applications (including word processing, spreadsheet, presentation, and drawing programs) for Mac OS X. Based on the OpenOffice.org office suite, NeoOffice/J has integrated dozens of native Mac features and can import, edit, and exchange files with other popular office programs such as MicrosoftTM Office.

Mac Slash has some information, and you can also check it out on the Apple site download section. So it looks like the reason that there's been no development of the Aqua version through OpenOffice.org is because they have been busy elsewhere. Any of you Mac heads want to give this app a try and let everyone know about it?