Windows 8 has been a ROARING success no matter which way you cut it. 100 million in 6 months is way more than any version of Mac OS or Google Chrome OS will EVER sell.
100 million licenses sold to OEMs and the retail channel. Actual sell-through is unknown. But even if we use these numbers, Windows 8 is much less of a success than Windows 7. Four years a go, there were half as many Windows PCs as there are now, but Microsoft sold the same number of Windows 7 licenses in the same amount of time.
Also, if PC sales are any indicator, consumers and businesses alike are not interested in Windows 8. Back when Windows95 was introduced, people were camping out in front of computer stores to get their hands on it. Are you willing to bet what percentage of Windows 8 sales are boxed upgrades?
This isn't four years ago. There are viable alternatives to a Windows PC, there's less reason to upgrade four year old computers, and people are understandably hesitant about buying a Windows tablet. It will take time for Microsoft to overcome these factors. It's still a success when you account for these things.
