Thanks for this improvement, Eric!
Unfortunately, there is a shortcoming if you drag the image while it is scaled up. You have to touch the image 2 times to scale it up again, because scaledUp only gets updated in touchUpInside:, which isn't called if you pan the view.

This can easily be solved if we implement it as follows:

    if (self.isScaledUp) {
        [self scaleDownView:sender];
        return;
    }
    [self scaleUpView:sender];

and set the proper scaledUp value in scaleDownView: and scaleUpView:.

Does this look good to you?

Another solution can be to simply pause the animation in touchDown:.