So much cleaner and more consistent. Classic classes are gone for good! Unlike with other languages (which I won't name for fear of offense!) I think Pythonistas will actually migrate to this much improved Python (well, forgetting the 10% performance hit) especially as such focus has been put into making tools to make it easier, unlike with PHP 4->5 (oops..!)
Just for kicks, try getting a stable webapp stack running on 2.6. I'm still not near ready to put that into production (and I run tiny, tiny websites).