- Store and serve application resources locally
- Store data locally in a fully-searchable relational database
Please note that Google requires Windows XP as the minimum requirements for Windows platform as this is the Windows version that has Internet Explorer 6.0 as the default (which of course the minimum requirements for browser category besides Firefox). This new service is not only for Windows only, since it's also available for Linux and Macintosh platform.
Meanwhile browser supports still needed in order to maximize the functionality of working offline. Mozilla will add this feature on their next 3.0 release, but i don't know about other browsers.
Soon, most web application can be cached and we can work offline.