Python 2.5 adoption

[Joseph Turian]

How widely adopted is python 2.5?

We are doing some development, and have a choice to make:
a) Use all the 2.5 features we want.
b) Maintain backwards compatability with 2.4.

So I guess the question is, does anyone have a sense of what percent
of python users don't have 2.5?

Thanks,
   Joseph