What really put me off a few years ago, on Linux, was the Uber-Geeky depths I had to plumb to get answers, drivers, and other stuff to work properly.
When it reaches a stage where you can just install it, and it works with your hardware without much tweaking, it will give MS a run for its money.
Now the idea of another large company. like Google, developing another OS is interesting- there's got to be a market for it.
Back in Windows 3.1 days, IBM came up with a brilliant idea called OS/2 for Windows. Within a few weeks MS came up with a patch to fix some esoteric problem with Windows 3.1, that by some cosmic coincidence broke OS/2 for Windows.
The lesson is it will take a miracle to unseat MS. They are positively evil and make shoddy products that make GM cars look like high quality.