I use it every day at work. We support multiple sites and so having multiple windows VMs on my corporate windows laptop allows me to be VPN'ed (using a mix of VPN clients) into multiple sites as well as into corporate at the same time. I mostly now use W7 VM's, but I still also have 5gb sized XP based VM's that run with only 192MB memory allocated per VM which makes it easy run lots of these as well as being easy to back up and use on other systems. All the VM's have the tools I need for any of the sites I may connect to.
AFAIK, there isn't any other free alternative for Windows systems, and since the company won't pay for VMWare It works well for me.