After further investigation and deliberation, I believe that we need to revert the built-in Tcl/Tk from the OS X installers for 2.7.6 and 3.3.3.  The contributing factors:

1. As implemented, we now know that the built-in Tcl/Tk breaks source installs and/or binary package installers for PIL/Pillow, matplotlib, and, by extension, pandas.  These are all widely-used projects and are important customers of the OS X 10.6+ installers.

2. With the recent release of OS X 10.9 Mavericks, there is now a critical problem (Issue18458) preventing interactive use of the current maintenance release installers (3.3.2 / 2.7.5) on 10.9.  New releases are needed as soon as possible to provide fixes for this, a few less critical 10.9 issues, and general bug and security fixes for all platforms.  So it is not appropriate to delay 3.3.3 or 2.7.6 to attempt to fix the incompatibility issue.  (Fixing the built-in Tcl/Tk for 3.4.0b1 or for future maintenance releases are separate open items to be tracked on Issue15663.)

3. Updated Tcl/Tk 8.5 installers for OS X are now available from ActiveState (8.5.15.1) which include the Tk patch for the 10.9 "screen refresh" problem originally seen with IDLE and patched in the built-in Tks of the 2.7.6rc1_rev1 and 3.3.3rc1_rev1 installers.

One positive outcome of this is that we are more aware of the interdependencies of some of the projects using the python.org installers.  As a result, I am adding to the python.org OS X installer testing and release processes additional "quicklook" regression testing using some of these projects so we have a better chance of catching issues like this one earlier.

Another positive is that it shows that there are members of the community who are taking the time to try pre-releases and that such testing *is* really important.  Thank you to all of you who have been doing so and reporting issues.  And a particular thank you to Piet for calling attention to this one.