I'd like to propose a few modifications of turtle.py for the transition
from Python 2.6 to Python 3.0, which would result in a cleaner interface
but also in some - i think marginal - incompatibiliy: 

1) drop from math import *

2) delete the methods Turtle.window_width() and Turtle.indow_height()
(They are mereley transferred from Screen to Turtle and are imho generic
Screen.methods. So they will still be present as Screen methods and as
functions. In fact this proposition has a didactic background - on
should teach to differentiate between Screen- and Turtle-methods as
belonging to two completely different types of objects, and the only
realistic reply to the student's question "Why do Turtle objects have a
window_width() method would be: "for historical reasons!" When, if not
now, is time to make changes like this?)

3) The same is valid for Turtle.tracer() as tracer controls in fact
Screen-updates and not Turtle updates. (The only difference is, that
Turtle.tracer cannot be deleted, because it's (currently) used in
turtle.circle(), so I'd propose to rename it to Turtle._tracer() and so
delete it from the public interface.  Of course tracer() will also
remain present als Screen-method and as function.

Pros and cons?

I have prepared a file with these changes which could be used for
porting it to Python3.0. So if everybody agrees, I could upload it.
Regards,
Gregor