Unfortunately, this is the canonical question that's so open-ended we
cant really provide much help (except for Cathedral in Bazaar link).
are you going to have to migrate DBMS, O/S or between ruby or Rails,
mod_ruby releases, are you worried about conserving sessions,
bandwidth, database accesses, page refreshes, um, money?  Security?

And in the past i've found support at Textdrive outstanding, on their
forums and by email.