Hi David,
My main crit would be that I prefer much less stretch prior to impact. There is a tendency for the top of the ball to look like it has caught on something when the ball is moving so slowly. (Some animators teach to leave descending stretch out entirely.)
Stretch as "motion blur" was probably more important when they were animating on twos and if the ball was moving much faster.
During the time on the ground I've found i like to do the squetch asymmetrically... most of the time is spent squashing down and just a frame or two is spent stretching back up so that the upward leaping motion is as fast as possible in the available distance. I want to get the ball's mass moving upward as fast as possible so a gradual stretch up won't do.
Here's a small experiment I did to see how long i could keep the ball on the ground. This is verging on too long, the ball is starting to look stuck to the ground. But if you frame through the first bounce you can see the asymmetrical timing in action. Lots of time spent squashing down as the ball has slammed into the ground, then a fast leap up.
SquetchyBounc000.mov
However, I think you have the fundamentals of Bouncing Ball going well and should graduate on to the next exercise which would be a ball bouncing in an obstacle course. This involves proper handling horizontal motion and bounces off of angled surfaces.