Thanks, dpb, for jumping in. My apologies for coming across as if justification for the previous workflow were needed - I was just interested in understanding the workflow better.
I wanted to take a minute to clarify the behavior change, just because I realize there may be some confusion among other readers of this thread. R2012b preserves the ability to manage editor files either as a group within the editor container, or as individual system-level windows. This allows the choice between using the operating system to manage the editor document windows or the MATLAB desktop. Windows within the editor container can either fill the entire container or be tiled as before. The specific change is that windows within the desktop editor container can no longer "float" such that individual documents are overlapping each other, while still contained within the editor group. One alternative to this behavior is to undock individual editor files, managing their relative positioning as operating system-level windows.
I'm sorry if this has affected your work. If it has, please let me know. Any additional details about how it has affected your work would be greatly appreciated.