It looks minimalistic compared to things like Apollo or Slingshot, but maybe the minimalistic approach combined with the Google brand will be a winner.
This sounds like a great idea - allowing the user to work offline with effectively the same application as the online version if I understand what they are doing correctly. Then syncing of the data once online again. The key downside of using online apps is: what do you do when you're offline and need to work. Could this be the beginning of the solution?
Does anybody know if Gears contains spyware? I expect that it doesn't, but I don't really trust Google. I would never install the Google toolbar, so if I ask my users to install Gears, I would have to be sure that it is spyware free. It being Open Source might be helpful to avoid that problem, though.