I've briefly heard about it. I am more familiar with Tails which is an amnesic OS as well as Whonix which seems more similar to Qubes. Both Tails and Whonix route all network traffic through the Tor network and with Whonix, dns leaks are nearly impossible. Basically Tails is for live booting, Whonix for VMs, and Qubes for a full OS install. Neither Qubes nor Tails should be run in VMs.