Windows 8 isn't the cause of a slump in PC sales. Nobody having any spare money is much, much more like it. My customers tell me the same thing. Also worth considering is that the improvements in hardware performance these day's aren't coming in such great leaps as the were just a few years ago. Punters are looking at costs/benefit considerations, and concluding that an upgrade right now isn't worth it. Bob O'Donnell might be an analyst, and good for him. However, I install/maintain and design office systems for a living, and this is what I'm seeing and hearing. Customers are saying "What we have is OK for now", whether the consideration is financial, cost/benefit or even a bit of both.
I also believe that's the real cause. And to add, it's also true that Microsoft gets a lot bad critics because MS is the largest Software Manufacturer from Planet Earth. Other concurrent companies will even spend quite a bit of money to even push for more bad promotion. Fact is also that there isn't any free Press and that everything what's published is censored upfront and may also "sponsered" by some concurrent companies. I would never take any report as the Lord's last word for to be 100% true!