There is no 'standard' and I agree - the plethora of choices is a pain. As for an integrated 'two way tools' IDE for Python GUI's, I also wonder why there don't seem to be any out there - maybe because there are so many GUI toolkits no-one wants to invest in an IDE for just one of them.
Having said that, PyQt 4.7 with P3k will give you wonderful GUI's (as well as a lot of other powerful features). See http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/introduction.html - "This is the reference guide for PyQt 4.8.4. PyQt v4 is a set of Python bindings for v4 of the Qt application framework from Nokia."
PyQt is in widespread use and there are some good books on it: see
http://www.qtrac.eu/pyqtbook.html "Rapid GUI Programming with Python and Qt" among others (book is outdated a bit - needs to be updated for P3k).
There are 2 serious issues with PyQt:
1) It has some distinctly 'unpythonic' characteristics, being just a thin wrapper on the C++ Qt libs. But I recommended P3k-PyQt 4.7 because some that has been addressed in the 'latest and greatest' packages. Check out this post:
PyQt design issues
2) For commercial use there are pretty steep licensing fees, both for PyQt and Qt.
An up and coming alternative to PyQt is PySide from Nokia, another Python wrapper for Qt which is entirely open source (that doesn't include the Qt licensing though).
Knowing a lot about Qt is not a bad thing market-wise, and you'll get that from PyQt, so I'd give it (or PySide) serious consideration if you're trying to decide on one GUI platform to become expert in.
Regardless of what you choose, I'd suggest avoiding tkinter for the most part, even though it's 'out of the box' with Python, because it's extremely limited, and IMO it has a crude, outdated look and feel.