0.5.2 has missing/broken arch templates (and 0.5.3 isn't at PyPI)
pyapp-0.5.2 has only 4 prebuilt apptemplates: main-fat, main-fat3, intel, and universal, with no single-platform templates. Also, "intel" is i386+ppc+x86_64 instead of i386+x86_64.
I probably wouldn't have noticed this, except that MacPorts defaults to x86_64-only on 10.6, so when I switched from Fink to MacPorts, I ended up with an x86_64-only version of py2app, and can no longer build any apps.
It looks like this has been fixed in BitBucket for 5 months, and the fix should be in the 0.5.3 mentioned on the wiki (http://wiki.python.org/moin/MacPython/py2app), but PyPI doesn't have an 0.5.3.