I'm using 2.7.1, because that's what my Ubuntu 11.04 bundles (python -- version reports 2.7.1+ though, no idea what the + means). On the other hand, Ubuntu provides 3.2 packages via apt-get, so I'm in the process of migrating to 3k. I really like the focus on laziness in 3k (don't know if 'focus' is the right word though, but there definitely are more lazy features in 3k). E.g. it's great that map and filter return iterators now (yes, I use them, how Guido finds them confusing is beyond me).
To the OP I'd say: learn Python through 3.2. It's the best way forward, for the sake of yourself and others. The only way more modules can become 3k compatible is if more people use 3k. /Sigmund -- http://mail.python.org/mailman/listinfo/python-list