It would be useful to know exactly which files are rewritten during this process so that it is possible to convert those files to a new format when needed (eg. after upgrading the distribution or installing a distribution not available by default, ..)

For a Fedora 17-based image, it seems to rewrite :

/etc/passwd (whether or not a SSH key has been specified - which is a bit annoying as there's then no way to know the root password when a key has been specified)

/etc/sysconfig/network

/etc/sysconfig/network-scripts/ifcfg-eth0

Any other?

Is the distribution auto-detected by the configuration-rewriting script (so that it rewrites what it thinks works for that distro) or somehow the initial distribution used to create the snapshot is stored by DO as well?