down-side of cached mode

I have heard and read hand-ful of cached-mode issues. Not good to use when
Outlook is upgrade, works better with clean installations.

Has few calendar issues. Also the emails in outbox are not synchronized.

Have known all about good features of cached-mode, but in this thread, i
would like to know just down-side of cached-mode feature.

Or discuss Online vs Cached-mode.

Thank you!