Recently I replaced my old video card on my PC, the old one had something like 160 core while new one has 960. I plugged it in and nothing really noticeable has improved. Same with when I swapped my HDD's out for SSD's. In contrast when I was a kid, there was a night & day difference going from an old Apple ][e to a 286 chipset.

But I also believe that Apple's gouged out a large chunk of customers via ipads and osx based computers.

There's also the question of what is wrong with Windows 7 for anyone to leave it? I can't find supporting numbers right now, but how many years did it take for XP's user base to abandon it?

Additionally Valve is starting to prop up linux's weakest sales point and make the consumer friendly distro's gamer friendly.

I guess my overall point is that a lot of little bites and not one main culprit is responsible for eroding Microsoft's market share.