Thanks, Guy, for your input. An obvious advantage of this change would be to get rid of a file in the source tree. Are there more? The disadvantages I cannot really estimate, because I am not especially experienced with Python packaging. I can only read, mainly at http://pythonhosted.org/distribute/, that using distribute_setup already today supports the transition towards a better Python packaging structure. You seem to have made your personal decision of what you find reasonable ("this is how to do it"), so before accepting your change, I would appreciate some more competent comments on your motivation of this change and about this topic in general. Thanks!
We're very experienced with Python packages here, we have more than 70 packages on PyPI, all are uploaded in this manner.
The Python packaging documentation sucks, and it is not up-to-date, I agree (eh, distribute has been merged back to setuptools weeks ago and its almost not mentioned anywhere).
So in conclusion, out of all these options, I would recommend Distribute, unless your requirements are very basic and you only need Distutils. Distribute works very well with Virtualenv and Pip, tools that I highly recommend.
I would have recommended Setuptools instead, were it not for the fact that Virtualenv doesn't support Setuptools 0.7 with Python 3 yet. Once it does, I'll update this answer.
If you just want a simple source distribution, you can just use distutils, which is always available
BUT, if you want the option to build an egg if setuptools is available), then you should try importing it.
In the future Python will only use the new wheel format, but until then... trying setuptools and falling back to distutils is the best option, unless your setup.py is complex (building binaries/requires Cython/etc), and that's not your case