I remember this clearly as if it was yesterday, because I tried and failed to build a Messenger-compatible client. They defended exclusive access to the API fiercely.
Their attitude seems so petty now in retrospect.
You take risks and bets in life and business. Use the tools that give you the greatest flexibility and build a robust business. In this case, these announcements increase that flexibility.
While everyone here keeps complaining and debating Embrace/Extend/Extinguish, someone is embracing the changes and out-executing them. I know which I'd rather be.
But if we really need to be juvenile and discuss everything to discuss anything, Apple is a greedy, voracious company. They are never presented otherwise, and cynicism meets all of their activities. But it's open and honest, and Apple doesn't try to be who they aren't, and users don't treat their actions as selfless gifts to the world. We all expect almost everything Google does to somehow pull in more ad data, to pull people to the fold, etc.
It's only with Microsoft where this naive "oooh, whole new company. So good" nonsense appears, and it grows incredibly tiring and seems more like a bad astroturfing campaign.
And as you said, there is nothing new in this. The whole "hell freezes over" thing gets a bit old because Microsoft has done this same routine countless times before. When they are the underdog, seeing a fleeing userbase, etc, they pragmatically veer towards open and integrated. When they aren't, they close off and exploit. (see Microsoft's arrogance and hubris as they exalted in their success with the Xbox 360 -- early initiatives like XNA, their unloved community gaming thing...abandoned and left to die -- and now that they're losing with the Xbox One, once again that wonderfully open and accommodating company returns again. People pretend it's new.
Another example I would give is MSN Messenger -- Microsoft did a loud, public campaign, including taking out ads in newspapers, pushing an open messaging platform, interoperations, etc. Microsoft had just started to get into the messenger game, so of course they didn't want to be kept out via the network effect.
Then, of course, MSN gained users (being pushed on users, automatically configured, tends to do that). Microsoft made a complete 180 in approach. Soon they incorporated an expensive licensing program that third party apps had to use to interoperate with MSN Messenger, endlessly doing technical fixes to block third party access.
What happened to that gregarious, open and cooperative Microsoft that was taking out ads to implore AOL for blocking access? The situation changed, and suddenly it wasn't in their interest anymore.