According to Debian bug #399113 and linked discussion it is impossible to run a stable system on Xen without enabling PAE. It seems that no-one is considering the fact that a hypervisor that runs on both 32bit and 64bit architectures should be able to support 32bit systems with <4G of RAM (IE not using the PAE feature).
But instead to work around this bug the Debian developers have decided to just enable PAE. This is annoying for me as I have to either buy a new laptop or reduce my use of Xen.
I wonder what will happen if a Xen bug is discovered that only happens on PAE systems? Would that make Xen only an AMD64 thing?