We use XML package configuration files in our development and production environments, primarily to store connection info and relative path info. We store our packages in the file system, rather than in SQL Server, and execute them from the SQL Server Agent accordingly. We use environmental variables on each server to store the location of the package config files. While it seems a bit cumbersome at first, once it is set up moving packages from development to production as simple as drag-n-drop. If a connection parameter needs to be changed, it's a simple matter of editing the XML-based text file instead of modifying the value in the DB. Some would challenge the security considerations of this approach, but in our small shop it works well.