IM interoperability a must

One of my biggest pet-peeves about IM services are their proprietary protocols. If you're on AIM/iChat and your friend is on something else (Yahoo, MSN, etc.) you're hosed. Sure, there are a bunch of third-party IM clients available (like Adium) but they only interoperate for text - they won't do audio or video chats.
It's analogous to the HD vs. BluRay battles that are being waged over DVD formats right now. No one can agree to fully interoperate, so they're taking their ball and going home.

Then there was a glimmer of hope that a truce had been reached in IM interoperability battle when TechCrunch's Marshall Kirkpatrick reported that Microsoft and Yahoo agreed to make their IM services interoperate.

Microsoft just announced that today marks the first day that interoperability between its IM client and Yahoo! Messenger with Voice is available. Microsoft says this is the first time two distinct, global consumer brands have made their IM clients interoperable. The combined user base of nearly 350 million accounts is the world’s largest, the company says. IM interoperability took so long that I thought it was never going to happen.

The bad news for Mac users is that IT Wire's Stan Beer claims that Microsoft may drop Mac support for their messaging client:

An interesting piece of information to come out of the Microsoft and Yahoo messaging alliance is the news that Microsoft is still evaluating whether to include the Mac version of Windows Live Messenger in its interoperability plans.

It would be an absolute tragedy if Microsoft left Apple users in the cold with this great new feature (although there's always Parallels and Boot Camp). Microsoft should stop cutting Mac users out of their development plans and deliver a Windows Live Messenger client for OS X. Post a comment on the Yahoo! + Messenger Program Manager's blog if you feel the same way.
Now if only AOL would join the interoperability party, the consumer would finally get the IM service they deserve.
Is full IM interoperability important? Which IM faction do you belong to and why?