You've no idea what you're talking about.
I've found bugs in Ubuntu without even trying.
You only need to look at the source code repositories of any open source project, and the subsequent regular updates they roll-out to realise your "bug free" statement is utter nonsense.
No piece of software (OS or otherwise) can be bug free. It's the nature of software development. Software is designed and coded by humans. Humans make mistakes.
As the great orator D. Rumsfeld put it :
As we know,
There are known knowns.
There are things we know we know.
We also know
There are known unknowns.
That is to say
We know there are some things
We do not know.
But there are also unknown unknowns,
The ones we don't know
We don't know.
Until I stopped using Windows I thought all the problems were just normal... they aren't. Windows is a really bad operating system unless you have some compelling reason to use it.
Again, your personal experience. You appear unable to tell the difference between a localised problem and a problem with the product (i.e. Windows OS).
There are far more users out there who can demonstrate to you that Windows is not "really bad".
I'm a Mac OS supporter at heart, but even I have to admit that Windows 7 / Windows 2008 are actually half-decent operating systems going-forward. Of course some will always bemoan the departure of XP, but Microsoft are taking large strides forward to ensure that you will reap benefits from an upgrade. Yes Windows is not perfect, but it's not hideous either.
The problem with the Open Source community is just that, there's no clear course or direction. No incentive for people to contribute (a) quality code and (b) do so in a timely manner... because they are not rewarded (financially or otherwise) for doing so.
The whole linux thing is also getting out of hand, why does the world need quite so many linux distros ? It's not a good recipe for quality, reliability, efficiency or sustainability.