Hi Michal,
This is turning into a me too discussion. Which is fine with me.
First, I'd wager the view that Windows works fine for audio and video is based on a consumer perspective, where I basically agree, (less so since Vista)
In general (and I like to generalize) Windows works... for consumers.
Less so for hobby/pro work where stability and reliability are much more important here Windows breaks probably as often as Linux (though in different ways)
I do EVERYTHING in Linux. I've had the fortune of being able to use 99% Linux at work too. (At the moment this isn't true, which has caused me headaches, but also perspective)
As for audio work.. it's interesting that you find that RT kernels are a pain. Basically this is my view too. They tend to be broken one way or another, pretty much all of them to some degree... this view is reinforced by the steady stream of discussions about which patch to use.
For the type of audio work I do, recording mainly, I am quite happy with the standard ubuntu kernel. The occasional xrun happens, but very seldom during recording. Keeping the cpu load down and not doing any other work during recording (who would???) tend to keep things stable for me.
My 2 € cents
Robert