A few general comments on the thread:
First, I'd recommend VMWare if you want to also buy their support - its really quite good. Otherwise use vbox for desktop and proxmox for servers.
Second, vbox isn't 100% open source - IIRC, their usb bridge is closed.
Third, I dont really recommend using automated utilities to migrate machines (one exception). These tools don't do much more than do a full copy and sometimes mess with drivers. You can do this by hand with less errors. Now, the one exception is for a big data center. If you're constantly deploying and migrating machines, look at plate spin.