Martin, just to be clear: the purpose of the new feature *is* to allow the choice between 32-bit/64-bit and that is important.  My comment was that the downside of the submitted fix, as it stands, would be to not allow choosing archs only for pythons built with the 10.4u SDKs.  And with the 10.4u SDK, those pythons are and can only be 32-bit so the only arch choice there would be between 32-bit Intel and 32-bit PPC and the only environment where that could mean anything is on a 10.5 or 10.6 Intel machine where, in theory, it should be possible to run 32-bit PPC pythons in emulation mode. For pythons built with 10.5 or 10.6 SDKs (in as yet to be supplied python.org installers), then the arch feature allows choice among the up-to 4 archs in the build: 32/64, Intel/PPC.  The proposed fix doesn't alter that aspect of the new feature at all.  But the patch needs to be redone anyway so, if the weak linking is added, there wouldn't even be that very small drawback.

OS X multi-architecture executables: complicated!