For those who haven't run across soft-releases before, this is the
last step before the final release. Because things haven't been
finalized yet, some packages may change between now and the release. It
is not recommended to use soft-releases in production.
With Python 2.7, the Unified Installer works with this release with trivial changes. Really little more than would be required for a new 5.1.x release. I'll be doing some work to generalize the installer for use with either 2.7 or 3.x.
With 5.2, I'm also considering that we may drop the "works offline" feature of the installer so that we can pick up binary wheels from PyPI where possible. That will make the installer smaller and will help it to work in environments like OS X where the dependencies for Pillow and lxml are less likely to be easily available. We already do this for Windows.
Hmm, the tradeoff there is that it may cause problems if there is someone installing Plone in an environment without access to PyPI, such as an intranet without access to the internet or in a country that censors internet access.
My first thought is to leave the buildout_cache/eggs directory empty and have all the sources and universal wheels in buildout_cache/download/dist. I existing installers, buildout_cache/eggs has pre-cooked, non-binary, eggs and buildout_cache/download/dist has only the sdists for packages with binary components.