> One project I work on that has a 35mb XML file takes 15-30sec 
> to load into memory but subsequent parsing with XSL takes 
> less than half a second or so...

That must be quite a system.  When you say "subsequent parsing with XSL"
I guess you're not doing a lot of work in the stylesheet? 

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list