In the server world, and the technical user world, it's the preferred system. In the embedded world, it's way beyond any other OS. Your wireless router is running a version of Linux.
/johnny
In the server world it has a valid place. In the applications world and the arena of most corporate and home users it is not very user friendly to use and maintain; aside from the fact that the wide variety of most-used software is either not available or doesn’t work well on it. I now teach IT courses and Linux machines are more trouble than they are worth to set up and maintain. Developing applications is infinitely easier on Win machines. Our faculty who favor Linux are the ones who advocate command line processing and intricate scripting over GUI applications when most of us moved beyond that years ago.