Why would some features still show as "Overridden" even after running a full features revert with the force switch? Below are the commands I am running, for the sake of clarity.
drush fr-all --force -y
A feature or features may not revert for the following reasons as cited by some developers in the issue queue #744450:
Here's a known issue, http://drupal.org/node/860974
I am battling that one myself.
It does depend on what you are trying to override. The output of drush features-diff could be helpful for others to give you a more precise reason.