I have downloaded and installed Mark Jaquith's WordPress 2.0.3 Changed Files ZIP package. I have verified that the Changed Files ZIP package contains nothing that is not in the original WordPress 2.0.3 download, so it is safe to use as far as I can tell. Verifying this took more time than actually doing the upgrade! I think the WordPress release team should provide something similar, as this is a much more convienient way of upgrading for those of us with just FTP access to our web hosts.