It definitely depends on your system configuration. Ideally, it shouldn't break, but however I had it set up was not happy about the upgrade. Did you use the built in Mac python or a new install from Python.org?

I see he has python via brew. That might be part of it.

Someone pointed out on HN that Python gives segfault. He used a = 1000, a/1000 example. I did it on Python 3 and got the same error. It worked on Python 2 that came with Mavericks but thats about it. I'd think there are more issues.

I don't know why they should be, but when I restarted my computer after the update I was greeted with a big fat broken virtualenv install, so I wrote this guide to help anyone else with the same problems.