Multiplicity is geared for the power user who wants to control several computers with a single keyboard and mouse.
After installing the program, you'll be greeted with a simple setup process; designate your primary computer with the mouse/keyboard setup. Users should note that all their PCs must be networked via Ethernet or wireless so that Multiplicity can sync them all together.
Stardock's program will guide users through the setup process: simply log the secondary computer ID and passcode under the "Computers" tab in the primary computer. To set the secondary computer, users must also install the multiplicity client on the other computers. Multiplicity will immediately detect the secondary computer and sync your mouse and keyboard across all systems.
Computers are organized in a "grid." Users can move their secondary computers into any arrangement up to a 7x7 grid. The upgraded version supports up to nine controllable computers, but you can visually arrange your monitor and desktop setup in any horizontal, vertical, or combined fashion. I can imagine this being quite useful when grouping processes into dedicated machines, like rendering movies on one computer while browsing the Web or working on separate projects in another.
The overall experience felt seamless and even native: Multiplicity supports drag-and-drop actions as well as copy-and-paste functions across machines. Though there are some free alternatives that exist, like Mouse Without Borders or even Synergy, Multiplicity offers some advanced premium features that make it distinct, despite lacking some of the cross platform functionality of its competitors.
Users can switch between computers using hot keys or mouse buttons 4 and 5 (for those with 5 buttoned mice). Multiplicity gives users extra control over wrapping over screens and custom constraints to prevent unwanted screen switching. You can also set unused screens to darken and even show a status notification, indicating which desktop you're using.
Another feature that works well is the built-in audio sharing. Multiplicity allows you to send or receive audio playing to and from any computer in your network. It's a nifty feature for playing music around the house if you have multiple computer speakers set up in different locations.
Again, these are premium features, but it is also very possible to replicate Multiplicity's core functions with some readily free programs out there. That being said, if you have multiple machines running the same operating system, then Multiplicity adds some noteworthy functionality. The upgraded version executes what it claims to do and does it well for the most part, minus some expected incompatibility when managing different operating systems (like XP with 7). But if you're only running two machines, then the free version might be sufficient for your needs.