I always manually set the order of editor tabs. Since 12.1 came out, I'm noticing than when I re-open a project all the tabs are reordered.
I can't seem to find an option that might control this behavior. If there is one, please inform me. If not, I consider this a bug. In the past, tab orders were remembered and restored.
I use a vertically split editor window with tabs arranged vertically on the left of each editor pane.
IDEA: 12.1 #IU-129.161
OS: Mac OS X 10.7.5