I used to see a "Lock" icon on file (tab) if the file was not checked out.. I have been using IJ from version 4 or so.. just noticed in IJ13 that I no longer see that locked icon..
This helped me figure-out quickly just by looking at the tab .. if I touched the file.. now i have to go to changes view and figure out if it was changed or not..
What usability analysis made sense to remove this feature form IJ ?