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I use Linux since 2002 and actually hate M$. But yes, it introduced Ajax and changed the world. Gmail was revolutionary because it offered 1GB when 10MB was the norm. Not because of UI.
Microsoft introduced a proprietary technology only IE5 could use and changed the world? Google implemented in both a maps app (completely new UI, and WAY more novel use of Ajax than outlook) and a mail app a standard that worked across all browsers (also something missing in outlook). Google showed us that you can use a new piece of tech across all browsers. Microsoft showed us you could do something in IE, and only…
As to novelty: XMLHttpRequest was invented by Microsoft for Outlook Web Access. "Ajax" was invented by Jesse James Garret as a new name for XMLHttpRequest.
I remember the first time I saw someone use OWA on IE, thinking: HTF does that work? Then I remembered he was using IE and chalked it up to proprietary browser extensions, which was correct. Proprietary but useful enough that the other browsers eventually had to duplicate the feature, with different syntax.
That duplication is what made Google Maps (and later, Gmail) possible.
So, yes. Microsoft gets credit for this one. Not for the generosity of their hearts, but for doing it and making it work and dragging the rest of the world along behind them. That had been the tradition with browser tech since the beginning, with positive and negative effects. This was a positive one.
Definitely not a Microsoft apologist here. And XHR could have been better. But no one else cooked it up, so, they get some credit.