Since I can’t really make head or tails of the xend/xenstore and the virsh way of configuring domains to autostart, I’ve just settled with exporting the config files from virsh and converting them to the native xen format.
Like so:
virsh dumpxml hydrogen > /etc/xen/hydrogen.xml && virsh domxml-to-native /etc/xen/hydrogen.xml > /etc/xen/hydrogen && ln -s /etc/xen/hydrogen /etc/xen/auto/hydrogen
(Ok, the last step was by memory. But the syntax should be correct…)
Edit @ 30th Apr 2011: Apparently the syntax has changed. Converting from xml to native is now virsh domxml-to-native xen-xm /etc/xen/hydrogen.xml > /etc/xen/hydrogen