Cooperative threads have their uses but I find the lack
of real native pre-emptive threads a major issue in a
21-st century language.
We should consider the inertia of programmers from
C++/Java/.NET background. They are used to and
experienced in solving certain kind of problems with
pre-emptive threads, and it's just too plain
inconvenient to step back and try to cope with
cooperative threads.

The idea behind Python is that programming should not
be a pain, right?

This applies especially to GUI programs, where threads
are used to perform time-consuming work in order to
avoid the GUI from freezing (was I surprised the first
time I tried this in Python!)
Just look at some of the modern Python GUI
applications, found in some recent Linux distributions.
99% of Fedora's configuration tools suffer extreme
usability issues caused by their single-threadedness. I
hate using yumex because the GUI is basically frozen
for the half minute it takes to reload all repos I have
configured on my machine!!! I know there might be a way
to alleviate this particual class of problems by more
careful cooperative thread programing... but I believe
we need a more straightforward solution (i.e.
preemptive threads) and not workarounds.

I apologize if this issue has already been raised before.

Cheers,
darkprokoba