The stability of Apple's machines is mainly due to the fact they have full control over the internal hardware and therefore can test everything against a very small range of hardware (peripherals excluded).

The moment "non-Apple approved hardware" is used, there's a risk of it not working - as we've found out.

Now, MS on the other hand have to support hundreds of motherboard combinations, with hundreds of different hard drives, with hundreds of memory suppliers/sizes/typres... which, in all honesty, they do pretty well.