The ability to run Windows on Macs has massively increased the reach and popularity of Apple computers. But you need a virtual environment to do so and the choice usually comes down to either Parallels or VMware Fusion.
For developers this ability is absolutely essential, allowing you to run Windows and other operating systems all at the same time. But even for general users, the ability to access Windows for using certain Windows only applications or to play games is invaluable. Gamers may be attracted to using VMware Fusion but should note that it won't perform as well as Bootcamp because Bootcamp allocates all of your RAM and CPU to Windows (or whatever other OS you might be using) while VMware Fusion only hosts it within OS X.
Firstly, you're going to have to make sure you've got a lot of RAM installed because VMware Fusion is very demanding. A minimum of 2GB RAM is recommended for it to run smoothly and, if you're intending on running several other applications at once with it, preferably 4GB. It's also extremely CPU intensive so it will sap your battery energy in no time.
The user interface of VMware Fusion is excellent. It's a clean and intuitive Cocoa-native interface that Mac users will be familiar with. It allows you to launch your Windows applications from the Dock and switch between Windows and Mac applications using Expose. The developer has used high performance virtualization technology that allows you to simultaneously run 32 and 64-bit operating systems, use two processor cores at the same time, run certain 3D games (but see above regarding this), and utilize USB 3.0 devices.
Most recently its been updated for the demands of Mountain Lion and Windows 8. Windows 8 apps now appear in the OS X Launchpad and you can even receive notifications from Mountain Lion’s Notification Center in Windows 8. VMWare Fusion 5.0 has also been optimized for Retina displays, USB 3 connectivity including Thunderbolt support.
One major downside of VMWare Fusion, however, is that it doesn't update automatically. Updating involves filling in lengthy forms on the publisher's site and then waiting for a link to be sent to you - not ideal. Those who rely on MacFuse will also be disappointed to realize that only the 32-bit version is supported in this release.
Overall however VMWare Fusion is a solid option for anyone that wants to run another operating system on their Mac - provided you have the specs.