Windows 8 is now officially available in Microsoft Pricelist starting this month. This product SKU now completely replaces Windows 7 SKUs from Pricelist, which mean its ok to say its released.
As far as the topic goes - yes its great offer to have upgrade offer opted from OEM
The final version of Windows 8 is not out yet. The guess now is August. This deal will be available from then until January 31, 2013.
The final version RTM was done on 1st Aug 2012 by MS and for EA customers and Microsoft Partners it was made available on 15th Aug 2012. I am on Win 8 Enterprise (I upgraded Win 7 Ent to Win 8 Ent). So far no issues and I am liking it better than Win 7.