Users of the VMware Fusion 3 tool for running platforms such as Windows within Mac OS X can look forward to a surprise under the Check for Updates menu. The company has released a fairly major 3.1 update focused on performance, its Unity feature, and support for more and larger virtual machines.

Leading VMware's list of improvements in Fusion 3.1 is performance. The company claims that the new version provides a 35 percent boost in application performance over Fusion 3.0. Likewise, scrolling and 2D graphics in Windows Vista and Windows 7 are almost four times faster than in 3.0, and 3D graphics performance is up to five times better. VMware Fusion 3.1 also now supports hardware-accelerated OpenGL 2.1 under Windows Vista and Windows 7 as well.

VMware also touts improvements to Unity, Fusion's feature that lets Windows apps run on a Mac outside of the Windows desktop and toolbar interfaces. VMware Fusion 3.1 adds support for overlapping windows in Exposé and minimizing apps to the Dock.

There are plenty of other new features and improvements in VMware Fusion 3.1, including an easier way to tie USB devices to your Mac or VM, a faster Migration Assistant, compatibility with new guest operating systems like SUSE Linux 11 SP1 and Ubuntu 10.04, and support for virtual hard disk sizes up to 2TB in size.

VMware Fusion 3.1 is a free update for existing owners of version 3.0. A free 30-day demo that requires an Intel Mac running OS X 10.5.8 or later is available for potential virtualizers; a full license costs $80.