Seriously? OK:
Orange France memo confirms September 15th was "Mango day" | wpcentral | Windows Phone News, Forums, and Reviews
Windows Phone FaceBook page changed for Mango | wpcentral | Windows Phone News, Forums, and Reviews
(Why update it early at all? And funny it was all ready to go on the 16th eh?)
Microsoft shows off Tango Video Calling | wpcentral | Windows Phone News, Forums, and Reviews
(released on the 15th)
Mango RUUs available in Taiwan | wpcentral | Windows Phone News, Forums, and Reviews
New Windows Phone 7.5 commercial nails it. Touts Metro Design, elegance. (Plus eBay Live Tile) | wpcentral | Windows Phone News, Forums, and Reviews
(mango-centric web ad for developers - released on the 14th)
Belfiore, Watson implore devs to update apps as Mango draws near | wpcentral | Windows Phone News, Forums, and Reviews
("*cough*now*cough*" - wonder what THAT means, eh? Fall? Two weeks time? No rush?)
Windows Phone Mango update imminent | wpcentral | Windows Phone News, Forums, and Reviews
In summary: you have Microsoft staff telling devs to get mango apps submitted (in their own words) "NOW" before the 15th, you have a soft launch in Taiwan scheduled for the 16th that went ahead, you have a load of official mango-centric promo videos and adverts and site updates happening on the 14th, 15th and 16th, plus countless mango apps being released into the marketplace well in advance of the 15th (I lost count at about 8, and that's just the ones featured on this site over the past week or so), you have carriers round the world all announcing they're ready prior to the 15th and to top it off you have a seemingly genuine email from a french carrier actually stating the 15th in black and white as the launch date.
Could all this be a massive coincidence? Yeah, it could. But in my opinion, there's enough there to make me personally think that there was a build-up to a possible global launch on the 15th which was then nuked for some reason. The actual date is actually irrelevant - I just think that as quite major software launches go, it's not been handed as well as it could have been and public expectation has not been handled as well as it could have been. That's it - that's my entire beef. I'm not annoyed or angry or anything - I just think it could have gone better.
You may disagree and see nothing here but coincidences and people getting their hopes up based on nothing at all but rumours; that's your prerogative.