Plenary Keynote: Guido van Rossum, "Python 3000 and You"
Matz (the author of Ruby) has a great quote, "Open Source needs to move or die."
Python is 18 years old.
Py3K will bring more predictable unicode handling.
It will be a slightly smaller language, since they're getting rid of a lot of things such as the difference between ints and longs.
One goal is to remove common traps. There will be fewer exceptions to rules.
Some changes, such as changing print from a statement to a function, are aimed at allowing future evolution of the language. Afterall, it's a lot easier to add another keyword argument to a function than it is to add new syntax related to the print statement.
Python 2.6 will be around and supported for about 5 years, so there's no rush to convert to Py3K. Take your time!
One strategy for open source libraries is to update their Python 2.6 code in such a way that the Python 2 to 3 converter can be used over and over again. That way, they can provide both a Python 2.6 and a Py3K release.