Fragmentation and stagnation, despite some assurances to the contrary
I use Python both professionally and for fun (and C and C++ professionally) and don't get this impression at all. Major upgrades to shipped languages take time. The willingness to impose one-time incompatible changes for the sake of long-term improvements takes guts, and can certainly go wrong, but can very well be worth it.
As someone who worked in C and C++ pre-standardization, I recall (perhaps erroneously) that the new standards broke a fair bit of existing code, albeit in minor ways. And of course Microsoft's broken C++ compiler in Visual Studio 6 resulted in a vast amount of borken code when they finally caught up to the rest of the world.
That said, I haven't moved to Python 3 yet, although I believe all the libraries I really care about have now migrated. I tend toward late-adoption, though, and my sense of the Python community is that everyone accepts we are eventually going to move to 3. Big changes take years, so it's no surprise that lots of developers are still on 2.x. The real watershed will be when a few major libs (wxPython, say) drops 2.x support.
In contrast, my impression of Perl 6 is that it's the language of the future, and always will be. It appears so different from Perl 5 that it's a little weird the same name is being used, and it has mostly resulted in sucking the oxygen out of Perl 5 development.