Here's a clever little trick you can use with the Preference Recorder in the Workspace Mechanic for Eclipse:
Let's say you built a Preference Task that you want to apply to your workspace. So you put the .epf file in one of the registered directories.
Turn on the Preference Recorder. Let the Workspace Mechanic scan for, and run tasks. It should find your new .epf and offer to apply it, and any other tasks that fail the evaluation phase. After the repair phase completes, turn off the Preference Recorder and see what changes were actually applied.
Kind of fun. If you find that kind of thing fun.