Ok, so it is a sneaky subject 😉
But it’s true. In a positive sense too: You can now use Google Gears for full Gmail offline experience. While you are online, all your content is in sync. When you go offline, Gmail works through Google Gears to allow you to read, star, reply and compose messages. When you get back online your changes sync up, mail is sent and operates very much like Outlook in the offline mode.
While Gmail has supported POP3 and IMAP for a long time, giving you the ability to take messages offline and continue to work, this new experimental feature is significant because the flags and message status indicators are updated on Gmail web site instead of just in your client. Personally, I use Evolution for my Google Apps.
This is still experimental so it could warrant waiting for a solid release.
Disclaimer: I’m a paid Google advisor in another area.