Tkinter is Python's "default GUI framework". At least, that's what they continue to claim (https://wiki.python.org/moin/TkInter), and it's the GUI library I ran into first when I first learned Python.
How does it look and feel once you get started? Well, let's just say it's a bad sign if a GUI framework website has no screenshots. Even with increasingly hacky theming engines layered on top, it still is hard to get anything feeling close to native: http://tktable.sourceforge.net/tile/screenshots/macosx.html
Go ahead, you can start laughing...
(for anybody that is saddened by the above, there are thankfully binding libraries for Qt and Wx, both of which do get you fairly decent cross-platform widgets from within Python, and either of which would be better default GUI libraries in 2014.)
People have been making the argument that QT or Wx should be the default for a while, the problem is and remains A: licensing or B: complexity of shipping "batteries included" distributions. For A, PyQT's license might surprise you: [1]. Python can not distribute this with the rest of the essentially-BSD-licensed Python distribution. For B, for instance, none of the linux distributions particularly want "Python", which is often a base requirement, to pull in either of Wx or QT, both of which are quite sizable, and require their own stack of other things to come piling in too.
It's sad, but I'm not sure how to resolve the problem, and nobody else has been either in the past 10 years.
The solution is to stop shipping with batteries included and let people install via pip. Python could have an official opinion on what the best libraries are (might not be such a bad idea, actually), but they shouldn't bundle them unless they're very, very stable, tested and almost unchanging.
Requests might make a good addition to the standard library at some point. PyQT definitely shouldn't though.
PySide (thanks lambda) appears to be LGPL; "better" than PyQT, but still not shippable in the core Python distro without changing the license of the core distro.
I think that's as "good" as a QT binding can be, too; QT itself is LPGL (or commercial license).
PySide, though PyQt still has certain advantages if you can live with the licensing (which is either GPLv3 or a £350 per developer commercial license).
> "... they should have had at least one killer feature"
I already commented on it and I agree. Python 2 is great and Python 3 is a little bit greater. But just not better enough to switch.
> Or if Python 3 had included reliable (and updated) package and environment managers;
I remember being at Pycon and distutils2 was announced. There was an aura of coolness, enthusiasm and hope in the air. Someone asked "but what about RPM packages?" they laughed at him and Tarek hid behind the podium in a funny gesture. Years later I am still using the default old included distutils package and building RPMs with it.
Or if Python 3 had included reliable (and updated) package and environment managers; and/or a default GUI framework (QT maybe) - out of the box.
The fragmentation between Python 2 and Python 3 is killing the language. Not to mention the community. Python needs a united front.