Don't worry Windows 8 users, the update is still free
Anyone rocking a legal copy of Windows 8 is eligible to receive an update to Windows 8.1 free of charge when it's made available on October 17, 2013 (two weeks from this Thursday), though if you haven't made the leap to Microsoft's touch friendly operating system, you can jump straight to Windows 8.1 for $120. That's the cost of the full version of Windows 8.1, and it's now available to pre-order.
Bear in mind that Windows 8.1 is not intended for installation on machines running Windows XP or Windows Vista. If you're running one of those OSes, you can purchase a copy of Windows 8 and receive and the Windows 8.1 update free of charge when it's available.
For those of you running Windows 7, Microsoft promises your files will "easily transfer" when installing the full version of Windows 8.1
Windows 8.1 brings several improvements to Windows 8, not the least of which is the return of the Start button (though not the Start menu). It also introduced an improved browser in Internet Explorer 11, more control over tiles, improved multitasking support, and more.