To answer the question, the ease of virtualization depends a great deal on the tools you are using to create the environment.
As with almost anything dealing with computers, there is more than one way to achieve the virtual environment you desire. Some of them are better than others.
You can use a software like VMWare and get the job done. And you can partition your server and load each section with its own operating system, which is the most typical way to approach virtualization. But you can also virtualize a desktop, or multiple desktops, within a network (rather than virtualize a server).
Desktop virtualization is not as easy to achieve as server virtualization. But in some cases, it might be more desirable. After all, you can develop a more flexible environment for an individual user in your company, or a group of individual users, without affecting the computing resources of the rest of your company.
Is virtualization easy or difficult? That depends. Are you trying to create a one-size-fits-all environment, or are you trying to make your network easier to use for everyone who uses it? Try the right tools and it is a lot easier.