Xen update
I found a machine which is not so ancient and did some tests with Xen on it.
Kernels
First was some tests with different Linux kernels and hypervisors (3.2 and 3.3). I have to say the overall compatibility got better. As unpriviledged domain (DomU) only one of the kernels failed, the one from Etch (2.6.18-6-xen-686) on the x86_64 hypervisor because of missing setup code.
For the operation as priviledged domain (Dom0) it looks not so good. The 2.6.18 from Xen 3.1 works mostly, the Lenny-targeted 2.6.26 is a little bit picky about the hardware and seems to work better in the 64bit variant, the 2.6.18 from 3.3 is old but rock-stable.
Stub domain
Xen 3.3 adds the possibility to move a the qemu which provides the emulated hardware for full virtualized domains in its own (paravirtualized) domain. The documentation is not really complete and the whole thing rather fragile. Error messages from the emulation domain are swallowed and depending on the config it also likes to crash.
It wants a new service, a filesystem backend, which is implemented in a root process in the dom0, even if it is not needed for operation. This service is not configurable, exports anything in /exports and allows writing, the code have similar quality then qemu.
