Well I would strongly dispute that anyone other than the developers
expected this. The release documentation states:

"The net result of the 3.0 generalizations is that Python 3.0 runs the
pystone benchmark around 10% slower than Python 2.5."

There is no indication of an order of magnitudes in read/write slowdown.
I believe that this issue is extremely serious! IO is an essential part
of a program, and today we live in the world of gigabytes of data. I am
reading reports of even more severe io slowdowns than what I saw:

http://bugs.python.org/issue4561

Java has had a hard time getting rid of the "it is very slow" stigma
even after getting a JIT compiler, so there is a danger there for a
lasting negative impression.