Many organisations end up running several different versions of Microsoft Office on different laptops and desktops. Sometimes it is the need to maintain a particular version because of legacy apps that require the particular version, or would need significant re-writes or updates in order to use a new version of Office. I can understand that, though I don't agree with it :) With that in mind though, do you have just one Enterprise Vault Outlook Add-in version deployed across the board, or multiple? Do you need to have an older version of Add-in because of a clash between a different Outlook Add-in and the Enterprise Vault one?
Personally I'm all for deploying 'one' version, but I know that there reasons why organisations might end up with more than one - I just wondered how frequently multiple versions were deliberately deployed.