You make a valid point that certain things break and take coaxing and searching message boards to work. That's definitely bad.
The point I would question is that of the UI. There are many aspects of OSX that are weird -- the mouse tracking, installing applications, setting a background color for your desktop, bringing up a terminal. Other issues exist for Windows. I can see how it's hard to detach yourself from something you're used to, though.
Those are going to be the two main issues in getting Ubuntu off the ground with average users. Having shit not break, and being close enough to users' existing habits to make the switch easy.
My hunch is that things are pretty close to where they'll end up. Linux will be an attractive alternative among techies, hobbyists, and average folks with spare/old machines. Microsoft and Apple will respond by cutting prices, and in the end, won't lose a substantial share of the market to Linux on the desktop, but suffer decreased margins. The user wins.