Depending on 32/64bit version of your OS, 32/64bit of your Outlook, Outlook version, Exchange version you could encounter problem in Outlook when Outlook plugin is installed (even if Outlook AutoProtect is disabled via policy). Is not something you'll sure face, but it could happen.
For my experience, in huge environment if you don't have the possibility to test all the possible combinations, I suggest not to install Outlook plugin at all (first installation or upgrade).
It's better to take your time in order to test different combinations and then, if you're sure, install the plugin.
Security is sure important but, most of the time, email is a service so crictical that you cannot stop or make unstable.
Best practice:
- test
- re-test
- re-re-test
- wait a little bit
- re-test
- ok, deploy