Yeah, I don't think that trait distinguishes Python from Ruby or Perl, or even Java, for that matter. Cross-platform compatibility is an advantage of interpreted languages in general.
This is one of the few things that irks me in programming communities, often you'll seen criticism or praise of a point in a language, and then some language lawyer comes and talks about what said language can do in theory, rather than looking at the practicalities of actual, real world implementations, the community and culture surrounding it and so on. No one gives a crap if any dynamic language COULD be made to work the right way on many OS, people care if the work is done, not if it COULD be done.
The worst offenders are of course people victim of the sufficiently smart compiler curse.
I have 163 packages in my local pypi, and they work fine on Linux, Windows, and OS X.
Luckily, most such packages (the popular ones at least) can be obtained in other ways (PIL through a win only download, or get a pure-python alternative like msgpack-pure-python).
Then comparing apples to oranges "I use Ruby for light scripting" vs "widely deployed desktop app with users from the three major desktop systems (Windows, OS X, Linux)."
This kind of behavior is a serious annoyance in online discussions.
If you were actually here to contribute, you might give a concrete example of why Python is more cross-platform compatible than other interpreted languages (because someone built a better Windows GUI toolkit for it?), but if you just want to put down and feel smarter than someone you don't know, you're wasting your time and keystrokes.
The fact that you actually bothered to count how many characters I typed strongly suggests the latter.