So this is a collection of things I came about when trying to get a Debian GNU/Hurd virtual machine running with kvm. Most of it is properly documented if you manage to find that particular piece of information.
Kernel Version
Due to a bug in linux 2.6.37 and .38 hurd will only boot if you supply -no-kvm-irqchip which is not that easy if you are using libvirt. A wrapper `kvm` script in the PATH will do, as will using a 2.6.39 kernel.
sudo
sudo will hang before returning from executing some command. I'm now using screen and sudo -i which keeps you a working tty gets you root and hasn't caused mayor trouble yet
sshd
openssh-server won't come up complaining about missing PRNG – and indeed there's no /dev/{u,}random in the default install. fix is to install random-egd from ports.