It's difficult to say "don't use Python 3.0" without being rude to the developers, as the code seems to be of very high quality. Now that Python 3.0 is almost here (release candidate 2 is a week old as I write) we should encourage people to use it, but only under well-defined circumstances. Here is some text I put together for inclusion in the release notes, to give people guidance about when and why it is and isn't appropriate to use 3.0. I would welcome further ideas to refine this text.
Readers should note that this release has significant backwards incompatibilities with the 2.X series, both at the language level and also in the C APIs available to extension module authors. These have been introduced by design, with the goal of improving the language in the long term, but this situation has implications for production use.
Furthermore it is likely that there will be a considerable delay before some authors of Python packages and extension modules start to provide 3.0-compatible releases. There are significant hurdles to be overcome in migrating extension modules from Python 2 to Python 3.
For these reasons you are NOT recommended to rely on Python 3.0 as your main production Python implementation until you know that all supporting code is available in compatible forms. While every care has been taken in the production of the Python 3.0 release, and the release team feels that the system is of a quality comparable with the recently-released Python 2.6, the latter system is currently the recommended version for production use.
I hope that clarifies things, but I would welcome further ideas to refine this text and make it more helpful. One of the primary reasons for using 3.0 is to get a migration strategy ready. But 3.0 is undoubtedly not for everyone, at least not just yet.
