Another in similar vein is "I want to be able to look at Properties to see if someone has read my message." Commonly known around here as "snooping." People mourn and celebrate the loss of the "snooping" feature in equal numbers here.
With the possible exception of delayed delivery, these are all examples of "stupid legacy features of pre-Internet workgroup mail." They only work in an environment disconnected from the Internet where it is only possible to use one particular proprietary email client.
I'm not sure about appointment duplication. The user who noticed it was migrated weeks ago, and we didn't try re-migrating.
We are seeing a fair amount of
Bug 17509 - duplicate appointment created, as we deployed Outlook connector 5.0.2 on all desktops (over my objections).