Few things in collaboration will get people more worked up than a user experience change, especially when a contact center is involved. (Protip: do NOT anger the contact center gods). Here is a little story about firmware release 9.4(2SR1.1) (or 9-4-2SR1-1S or 9.4(2)SR1 depending on where you see the version referenced) for the Cisco 7900 series IP Phones and how it has caused grief for not only us, but other customers as well.
Cisco 7900 series 9.4(2)SR1 headset hell
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