Let me state that again, after January 31, the $39.99 upgrade price will end. Starting February 1 2013, the Windows 8 upgrade will cost $119.99 and the Windows 8 Pro upgrade will cost $199.99.
So you may want to order your Windows 8 today. $39.99 is a lot less than $199.99. Unless your just gonna have it sit on a shelf. (even then it is a lot cheaper)