For a serious long term project I'd certainly use 3.x, to be future proof. It'll probably take some sorting out compatible packages, but it prevents a technical debt. Also the added performance, features and cleanups are worth it.

For a quick hack I'd still use 2.7 because everything is compatible so it should be easier to get up and running.

I use 3.2 for almost everything.

I've built a couple small web apps, a few small PyQt apps, and a ton of utilities with it.

Only times I've used 2.x recently was when I needed OpenGL, and another time when I needed cgkit.

Basically the only time I use 2 is when I need a specific library and there's no alternative that runs on 3.

2.7

The switching point for me will be when django start support 3.x. Looks like Django 1.5 will add experimental support for Python 3.x. Then there will take at least a couple months for most of the vital packages to be compatible.

Building a webapp, probably still 2.7

However, I much prefer 3.x. Much cleaner, better stdlib, and unicode everything. If you do use 2.7, please please please use 3.x printing though (from __future__ import print_function)

I guess it is 2.7 for me so far. One of the things with 3.x is that some major python frameworks are still not supporting it (Django, Flask etc.)

2.x, because I mainly use it for web development (and some math/gfx stuff).

I use django- It gives no option for 3.x- Using 2.7 for my current project

2.7 for me. Mainly web apps and back-end scripting.

2.6, I use it with cx_oracle, for sysadmin tasks

2.7 - Because of Django (mainly).