It is one of those days and I don't remember when these many Microsoft products went into RTM mode at the same time. It's a great achievement. Congratulations to all the teams involved in these great line of products.

Visit the following Product specific Blog sites to get more details on key capabilities including new ones;

 

For SharePoint 2013
http://sharepoint.microsoft.com/blog/Pages/BlogPost.aspx?pID=1035

 

Exchange 2013

http://blogs.technet.com/b/exchange/archive/2012/10/11/the-new-exchange-reaches-rtm.aspx

 

Lync 2013

http://blogs.technet.com/b/lync/archive/2012/10/11/lync-2013-is-finished.aspx

 

Office 2013

http://blogs.office.com/b/office-news/archive/2012/10/11/office-reaches-rtm.aspx