I've developed an automation helper for Aperture which lets you set up complex workflows and tasks by building up a visual flowchart, which can then be saved and re-used, or shared with other users.
You can do a variety of automated exports, such as making subfolder formats based on metadata, for instance export folders based on ratings, or use different export presets.
Other tasks include find-n-replace in metadata, finding duplicate master files, showing all Albums that contain a particular Version etc.
If you're interested in trying it out, Aperture Assistant is curreently in public beta testing and can be found here:http://aperture-assistant.com
P.S. I hope to add an XMP importer at some stage.