Mac OS X Notes
Starting with 2012, Maya started altering the native window behavior on OS X to always keep child windows on top. Along with being counter-intuative to OS X users, this negatively affects the display of other Qt windows.
It is highly recommended that the following flag be set (in userSetup.mel or Maya.env) to restore the native windowing behavior:
If this flag is not set, the following window behavior will be seen:
Charcoal Editor Falls Behind Maya's Main Window (OS X)
When the Maya window gains focus, Charcoal will fall behind the main window. The Charcoal Editor window does not always remain on top of Maya's main window (on OS X). Although this is common in other OS X applications (and expected behavior by some users) it is a noted difference with Charcoal Editor.
Maya Floating Windows Display on Top of Charcoal Editor (OS X)
When other Maya windows are open (e.g. Hypershade, Hypergraph), they are always displayed on top of Charcoal Editor. This happens regardless of CE having focus and being displayed on top of Maya's main window. This only occurs on the OS X version of Charcoal Editor. A resolution is currently under investigation.
Maya 2011 OS X
What about Charcoal Editor for Maya 2011 on OS X?
Qt 4.5.3 (required by Maya 2011) lacks a couple specific methods required to accomodate some differences with OS X. Although this only affects a small feature subset, I consider it significant enough to not officially release Charcoal Editor for Maya 2011 OS X at this time.