Seven Client OSes That Could Replace Windows - Mac OS X
1. Mac OS X
In terms of application support, functionality, packaging and overall mind share, Apple's OS X poses the greatest threat to continued Windows dominance. The biggest roadblock to OS X's ascendancy is Apple itself. The company restricts its innovative OS from running on non-Apple hardware, which means that unless Apple manages to put most OEMs out of business, OS X will always be a niche player.