While reading the "Multiple version install" thread, it occurred to me that wxPython may benefit from a versioning scheme similar to the one used by the Apache Portable Runtime Project. See http://apr.apache.org/versioning.html for details.
In a nutshell, the scheme links backward compatibility with the version numbers. I couldn't find a description of the versioning scheme used for wxWidgets or wxPython, but it seems to be arbitrary, at least in regard to backward compatibility.
The scheme used by Apache APR makes it easy to figure out if a given application (A) is compatible with a particular library (L), if one knows the version of L that A was last "certified" to be compatible with.
Matthew