Hi Sail,
I've never tried it. Here's some conversations about it at Garden Web that you might find helpful and informative. The first one is an ad for the stuff.
http://search.gardenweb.com/search/?...ll&sp-q=Aerify
You can also visit this site I found from the Texas Extension Service. Scroll down to L5340 and click on 'View PDF' for 'Maintaining St Augustinegrass Lawns'.
http://tcebookstore.org/pubbrowse.cfm?catid=125
Newt
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.