There is really not many alternatives to a Microsoft Windows based system in an enterprise. Granted, many enterprises can and do run Linux variants as their web servers, some use it as email servers and few even use them as file servers, but it's not always practical.

As far as workstations are concerned, in the enterprise there are several core applications that companies rely on for daily business that do not have a version for alternative platforms, other than Windows. Another reason why some enterprises choose Microsoft Windows over other platforms, even if they have a choice is, Microsoft makes it very easy to central manage and control workstations and ultimately user behavior.

On the server side, using a Linux based machine as a web server can make business sense. It can, in certain situations, reduce support costs and costs related to software licensing, but on the other hand it can also increase costs due to having to hire a specialized skill set for web developers.

One of the main drawbacks to using Linux based machines as servers is there is no standardized central directory similar to the widely used and supported Active Directory as implemented by Microsoft. There are several directory services available, from a handful of companies, but no one central directory that integrates well with Windows based desktops (that usually are required to run business software.)

As far as home machines go, it really doesn't matter what OS you use. I have multiple machines that are not part of any domain, each of them run multiple virtual machines with various OS's and after using a variety of OS's as my main interface to the machine, I've come to the conclusion that the OS really doesn't matter. I can be as much productive on a Windows machine as I can be on an OSX or a Linux machine. Granted when it comes to Linux, you have to use some variant that has a nice GUI for human interaction; Because of this, one of my main workstations is a Ubuntu machine.

No matter what OS you use as your main interface, keep in mind you'll have to have a Windows based machine somewhere to run all the applications that won't run on anything other than Windows. So am I promoting Windows only, not so. The best thing I like about other, not so common, OS's is that you probably won't need an antivirus, eating up your CPU cycles that you absolutely have to have on a Windows machine (and don't believe it for a minute when some Microsoft senior executive says that Windows with UAC is safe without an antivirus!)