This has been bugging me for a looong time, but for some reason I only just now pulled myself together and did something about it:
Back in Hardy, I changed Ubuntu’s version of virsh (the command line utility for libvirt) to connect to qemu:///system if you had access to that, and fall back to qemu:///session if you didn’t. This saves you the trouble of adding -c qemu:///system to your command line (or setting VIRSH_DEFAULT_URI appropriately) every time you wanted to do something useful with virsh. The upstream default was (and still is, IIRC) to connect to xen:///, but that’s not really appropriate for us since we prefer kvm.
virt-viewer, however, never got the same attention. It still defaults to xen:///. Or rather: it did until an hour or so ago:
https://launchpad.net/ubuntu/jaunty/+source/virt-viewer/0.0.3-6ubuntu3. Enjoy. Err… Make that https://launchpad.net/ubuntu/jaunty/+source/virt-viewer/0.0.3-6ubuntu4. Go me.