To clarify: NLTK develop branch is compatible with Python 3.2+ for more than a year. NLTK 3.0a4 (http://www.nltk.org/nltk3-alpha/) is not released as NLTK 3.0 because of some pending API changes, not because of Python 3 compatibility issues.
i use NLTK with python 3.4 (and before that, 3.3); NLTK has an alpha release for pyhthon 3; i have not had any problems either installing it or using it.
Ok so why would I risk hitting even one incompatible library or have stuff break because those are dev experimental, untested branches. Why? What does Python 3 offer me except risk of breakage?