Hi, Stuart.
Romit didn't answer your question but I can share my experience with you.
AUSST only downloads updates to applications, not the applications themselves.
One word of advice; if you're using the built-in Apache web server and aren't familiar with it (I'm not, and find it to be frustratingly difficult to use, just like AUSST) point the AUSST tool to a directory within your existing web pages. That will save a lot of headaches.
-Brian