I for two [ID said it first] think it's not as bad as some will have you believe. Okay, Windows 8 has been slower than Win 7 on the uptake, but I think sales will improve when more people stop listening to the haters and realise the benefits of the platform; Skydrive; the ease of synching their phones and tablet to their home PC; the myriad of free and practical apps in the Store; the speed and ease of use.
There's more, but I'm not being paid to sell win 8... dig in and find out for yourself.
There's another factor that most assuredly had a major impact on Windows 8 sales... the very poor state and collapse of several of the world's economies. It wasn't a good time for anybody to be releasing something new, which is probably why Microsoft introduced the time limited $40 licenses, to help more people to adopt it without breaking the bank. Trouble was, the naysayers and so-called experts in the media karboshed it, and not even 40 buck licenses were going to change the damage that had done.
Another factor was the fad on tablets and mobile devices, smartphones, etc. Not only were they cheaper devices to surf the net and access Facebook, they were portable to boot. It was a convenience the world wanted, particularly the younger set, but from my understanding of people I know who purchased tablets, it wasn't an either or shift away from desktop PCs, but an as well as... they wanted/needed both. So no, in such a dour economic time, people who purchased tablets generally didn't purchase a PC as well, the majority simply couldn't afford to. Hence the low PC sales figures we keep hearing about.
True, the naysayers and detractors had an adverse effect on sales, but I think it was somewhat marginal compared to the effects of the GFC and the worldwide fad on portable devices. Perhaps Ms could have rode out the worst of the GFC effects, then incorporated the improvements of 8.1 before release, I don't know, maybe sales would have been better. In any event Windows 8 is here to stay... until perhaps the release of Windows 9.