Linux works. This is a very matter-of-fact statement, but it is one many people (myself included) make every day when they boot up their computers. It is not a perfect product, it would not be sensible to expect something as complex as an operating system to be flawless, but fact remains that Linux does work.
On the software side of things the open source community has done a very good job of making this clear, but the other half of computing, hardware, this movement has not been as successful. Every day Linux users encounter driver and compatibility issues which Windows users have not had to deal with for years. Read on over at XYZ Computing.