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 drush fl
A feature or features may not revert for the following reasons as cited by some developers in the issue queue #744450:
One way of that happening, that I've tried myself, is to have two seperatere features define content types that use the same CCK field. Doing that it's possible to have different settings for the same field for. That way one them will always be overridden.
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.
This may seem stupid, but make sure you have all the files for the feature. One of my files didn't make it to git so it kept showing overridden.