Maybe it's a good idea to make it easy to transfer sites to a different server by incorporating some sort of backup system in the CMS User Interface itself. I can image Silverstripe producing one big archive file containing all content / settings and code for a site which one could feed to a "virging" SS installation on a different server.
ps (Almost finished work on our first commercial SS site ! Will keep you posted!)
while this would be handy in a few scenarios (e.g. slow ftp-upload with 1000+ files), i see it as fairly low priority. it has more benefits in a complex system like typo3, where you can extract parts of the system, e.g. a module with its custom uploads, config and db-content.
silverstripe has always tried to keep the UI clean for authors, and get the developers to work with existing tools like shell/phpmyadmin and sourcecode.
migrating a silverstripe-instance is mostly just a two-line export with "tar -c mysite" and "mysqldump" :)
one thing though: it would be easier to have all modules/plugins/extensions in a separate subdir, so its easily detectable what to migrate.