I have Windows 8.0 which I tried out on my laptop (since switched back to Windows 7). Windows 8.1 came out and you download it BUT cannot save it as a separate file. It installs the upgrade. Something like 3.6gb to download. Who wants to download again especially if you have multiple computers?
If you download the ISO of 8.1 and try to install it, Microsoft will not accept your windows 8.0 license. They want another $100 to $200!!
http://windows.microsoft.com/en-us/windows-8/create-reset-refresh-media
Workaround....
http://winsupersite.com/windows-8/windows-81-tip-download-windows-81-iso-windows-8-product-key
At least Windows 9 is looking promising so far.... We will see.
Microsoft has saved me a lot of money in the last few years by not selling anything of value.