While installing RH6.2beta on a fresh system, I managed to partition the
disks such that mkfs/mount failed.  Rather than returning me to the disk
editing screen and letting me correct the problem, the installer popped up
the familiar python traceback window.

It seems to me that the user should never, ever see a python traceback.  A
non-technical user is simply going to be baffled (and perhaps somewhat
intimidated) by the error, and is unlikely to know how to recover.

One might argue that this is a beta product, so of course the installer
offers information of interest only to developers, but the 6.1 installer
was (well, is) riddled with problems (to the point that it's easier to
install 6.0 and then use rpm --freshen to upgrade) that result in the same
situation.