I have tested the export/import of a configuration before and now it works smoothly. You simply add the file to the folder for installation profiles and chose it from the drop down menu.
As a side note, if you are restoring a backup you do not have to go through the installation process because restoring the file will recreate all of the user's custom features.
I remember a couple years ago needing to change some details in the xml config file. First off, if the profile name in the setup.php file has not been change, then you might need to change it in the xml file so it will show up as an option in the drop down menu. The other detail was having to go through and use replace to swap my user name with "administrator" as the system would stall because it could not find my user name. However, I did not have to swap my name out the last time I created a test database which is a great quality of life improvement.
