On a question of just performance, how does Python 3 compare to Python 2.x?
I'd say any difference will be below trivial. For example, looping over a list will be the exact same.
The idea behind Python 3 is to clean up the language syntax itself - remove ambigious stuff like except Exception1, Exception2, cleanup the standard modules (no urllib, urllib2, httplib etc).
There really isn't much you can do to improve it's performance, although I imagine stuff like the garbage collection and memory management code  will have had some tweaks, but it's not going to be a "wow, my database statistic generation code completes in half the time!" improvement - that's something you get by improving the code, rather than the language!
Really, performance of the language is irrelevant - all interpreted languages basically function at the same speed.
Why I find Python "faster" is all the built-in moudles, and the nice-to-write syntax - something that has been improved in Python3, so I guess in those terms, yes, python3's performance is better then python2.x..
Performance: Python 3.x vs Python 2.x