Today, Microsoft, by most standards, hit it out of the part with its most recent quarterly earnings just as competitors Apple and Google did. But there is some gray clouds on the horizon. Dispite great Windows 7 adoption, Windows revenue is down. This would mark the third quarter of decline, pretty much in line with increases in iPad sales. And I reckon that Apple's sales of Macs and particular the 9+ million iPads that Apple sold (not shipped) and put into the hands of consumers will increase and we can expect Windows sales to further decline.
Another analysis of the Business Insider figure I brought to your attention was fault because it did not figure the iPad numbers. With the new figure, MacObserver pointed out that iPad accounts for almost 10% of PC sales.
And whether analytics firms want to categorize the iPad as a media tablet and not a true tablet, they cannot ignore much longer the fact that these "media tablets", particularly the iPad, is taking a piece of the PC pie. This is why Microsoft, 12 to 18 months (possibly more given how they chronically miss deadlines), is talking up a tablet version of Windows 8 tablets.
Redmond recognizes the fact that the iPad is a threat. And that threat was realized in its shrinking Windows revenue.