I saw a feature request for this one, and I wanted to add my strong support for getting this built into the next beta.
Undoing is probably the thing I do most often when I'm coding, and unless the undo can keep up with the speed of my decisions I end up wasting a lot of time holding down CMD-Z to get where I already knew I wanted to go. Being that I type in lots of trace statements to examine my code, this gets in the way of my debugging as well.
Thanks for listening and I hope that we can see this get implemented. Cheers,
Ben