From PC World:
Perhaps most exciting could be Firefox’s ability to support writing an e-mail in, for example, Gmail while offline, with the data sent later when a user is connected to the Internet again. Ultimately, Mozilla engineers are aiming for an integration between the browser and Web-based services that is as smooth running as a desktop application.
If this actually works out, Firefox 3.0 will be a real big deal, and leave others like IE7 still farther behind. It’s about time too, that web-applications started driving better browser development.