I ran the demo for a week, and liked Multiplicity.  The demo works well on the first installation.  Primary PC is Vista Ultimate 32 SP1 and secondary is XP 32 SP3.  Since I had another Vista Ultimate 32 SP1 machine that I wanted to run as another secondary, I purchased Multiplicity.  I uninstalled the demo versions from the 2 computers that had been running the demo successfully.  This is when the problems began. I downloaded the new, bought version of Multiplicity (not pro) from the link they sent in the email.  I ran the setup on my two secondaries first.  They seemed to install correctly.  After the reboots, the program gave the splash screen saying that Multiplicity was running and the machines would respond as secondaries.  Then I installed on the center computer.  I designated the machine as primary.  I chose the left computer as a secondary.  It seemed to find it.  Then I chose the right machine as another secondary.  It seemed to "see" that computer.  The name of the "left" computer showed in the interface, but the name of the "right" computer wouldn't show on the screen.  I finished the install and rebooted, thinking that maybe after the boot everything might work.  No such luck.  The primary machine doesn't see either machine after the reboot. I read through the support articles on the web.  I email Stardock asking for help.  I am busy, so leave the problem for the following week. On the following Tuesday, I get an email from Stardock saying that my original uninstall didn't work, and I need to uninstall again.  This time I uninstall on all three computers.  After the uninstall I reboot.  I discover that the uninstall doesn't uninstall.  There are all of the files left in C:\Program Files\Stardock\ThinkDesk\Multiplicity.  I try to uninstall again.  The uninstall doesn't show that Multiplicity or Stardock or Thinkdesk is installed, yet the Multiplicity icon is in the system tray and is still running.  I kill the services, I delete the c:\program files\stardock directories.  I kill everything in the registries that mentions stardock or that directory path. I reboot and make sure that everything is clear.  I attempt another install on all three machines.  Still the same results, but this time I CAN get the (vista) primary to talk to the XP secondary.  No go on talking to the other Vista machine.  By this time, the firewall has been disabled for all three machines, trying to rule out communication problems.  I still have the annoying problem that the interface will allow me to define either a left computer or a right computer, but not both at the same time.  After a bunch of hacking and rebooting, I can now either control a left computer or a right computer, but not flow from left to center to right.  I either get left and center or center and right, but never all three.  I read through all the support articles again.  I uninstall from all three computers again.  I see that uninstall doesn't uninstall. After rebooting and looking around, I see that all the files are still sitting in the C:\program files\stardock\thinkdesk\multiplicity directory.  I do a seach and destroy in the registry. I reboot.  I do a search and destroy in the program files directory.  I reboot.  I attempt to reinstall again, this time using the XP SP3 machine as the primary.  This time the activation fails because "Max activations is reached".  I fire off another email to support. 

This is way too much work for this product.

EDIT:  Update, I worked out my issues with tech support.  I now know that the Standard version can control the primary and one secondary.  The Pro version can control the primary and up to 6 secondaries. The pro version adds file copy between computers.  I now own the Pro copy and it is doing exactly what I need it to do with my 3 computers.  I have the center computer running XP Pro 32 SP3.  The two secondaries are running Vista Ultimate 32 SP1.  I can log in to the Primary computer, then move the cursor to either the right or left computer and press Ctrl Alt Backspace to then login to each computer seperately.  Once all three computers are logged in, the keyboard and mouse on the Primary computer control all three computers flawlessly.