In my testing with Pages '08 it worked just as advertised. I set the save interval for 45 seconds and as shortly after I opened a new Pages document it brought up the save dialog. I put in some text, waited a few seconds and then simulated a crash by force-quitting the application.
When I reopened the document, my text was there. Unfortunately, I've found that EverSave does not work quite as well with all applications. With TextMate, for instance, it insists on bringing up the save dialog box every time it saves, making it too annoying to be useful. Nonetheless, if you use iWork and miss auto-save, EverSave is a must-have.
EverSave is a free download (donations requested) from Tool Force Software.