One of my Debian boxes runs something close to stock etch on both dom0 and most of the domUs. I had a minor issue upgrading one of the domUs to lenny, so I thought I'd document it.
Most stuff works
I did the upgrade without much thought, and it didn't go entirely smoothly: it took a few iterations of aptitude dist-upgrade to get there.
I have a custom exim configuration, and the template format for the exim4.conf file has changed. I started from the new Debian file and added my own local changes again, that seemed to fix it.
libc6-xen is a bit odd
Before this tweak the logs are full of '4gb seg fixup' errors.