Well customers pay for it, use it and like it. That my book qualifies it as not broken. They can chose other software but they pick this one.
Also, just because unit tests cover the code and pass doesn't mean product is not broken. Two working units of code adding together in a system don't guarantee that system will do what it is supposed to do. So yes there is risk.
The bigger problem is that there are not tangible benefits of Python 3. That is its tragedy the way I see it.
And time-wise, it is pretty sad, it might take me less than a few days to work through it, but it is still not worth it.
Most important -- risk. Risk that stuff will break. One of the biggest ones is change to the .keys(), .values() to behave like iterkeys.
Also unicode vs byte strings.
Also time. And time = $ in most places.
So far need the benefits are just not there. It is something like this:
benefit(switch) = code_improvements - time - risk + possible_future_benefits
(time has an opportunity cost folded into it, if I am porting to 3 I am not working on other stuff).
So far benefit is either negative or just too small for me.