[Guido van Rossum]
I suspect that the people who complain that Python's rate of change is too fast are misguided. [...] So maybe there's only (or mostly) a problem of perception?
I use Python on a few systems and flavours, and Python versions are not the same on all machines. At places, people ask me to limit myself to 1.5.2. At home, I have 2.2, but 2.0 is currently the common denominator for the set of machines on which I do my own projects (I physically travel between sites). For one, I have no real problem aiming 1.5.2 or 2.0 instead of 2.2, when projects or teams require it. Despite I much enjoy most of the new features, I still have to be careful about various development contexts.
I would presume that for a newcomer to Python having to ping and pong between different Python versions, not firmly aware of the differences, might feel irritated by things working here, but not there. This is just an hypothesis, as I did not experience such an irritation myself: because when one knows which version has which features, there is no real problem.
I guess the difficulty comes from the time evolution takes for new versions of Python to get installed universally, so new features are just there, dependably, blindly, everywhere. This means a few years at least. The difficulty does _not_ come from forward incompatibilities (there were a few around sockets, say, but these were simple things, not really worth complaining about in my opinion), in my experience, forward migration has been either very easy or just fully transparent.
The current pace of change does not look unreasonable to me. I wonder if the perception would not improve, if there was a bit more documentation or publicity about what users should do about version inter-operability. If users understand what they choose, they will less likely feel changes as imposed to them. Maybe! :-)
-- François Pinard http://www.iro.umontreal.ca/~pinard