I use both, really. I started by learning and using Python 3, but I ended up using Python 2 much more often compared to Py3. Not because of the functionality of the language, but because most software that embeds Python or is extendable in some way is usually using Python 2. + There's the whole libraries issue (or the lack of them).
But I have to say, Python 3 is a sexy language, I can't wait for more libraries to appear so I could focus more of my attention there. -- http://mail.python.org/mailman/listinfo/python-list
