As of today, operating system for Windows Phone 7 is complete, and released to manufacturing.  Terry Myerson made the announcement today in a blog post:

Today is the day that the Windows Phone team has been driving towards, and we’re very excited to say that we’ve reached the biggest milestone for our internal team – the release to manufacturing (RTM) of Windows Phone 7!  While the final integration of Windows Phone 7 with our partners’ hardware, software, and networks is underway, the work of our internal engineering team is largely complete. 

While much of the system has been publically shown already, the Windows Phone team has made some changes, according to an email we received announcing the RTM:

Since Technical Preview back in July, Microsoft has focused on the important task of finalizing the Windows Phone OS and added a few feature updates such as:

·         Made it possible for people to filter their contacts so only the Facebook friends they really know will show up in their contact list  

·         Incorporated the ability to “like” a Facebook post from the People Hub and delivered the ability to quickly post a message to someone’s Facebook wall directly.