Hmm -- so Adobe Apollo, Firefox 3, and now Google Gears are all going to address the same problem space?
Web applications bring your data online and make it available anywhere there's an Internet connection. But happens when you're on a plane or when you can't find a WiFi hotspot?
Google launched an open source browser extension for IE and Firefox called Google Gears that enables web applications to be available offline.
See the post for more details, e.g., on Gears used with Google Reader.