I used a US Shift controller with a 4L80 (also compatible with your 4L70E) and it was ten times easier to modify than the GM controller. You can do it straight from the controller or connect a laptop. I did not really ever do it from the controller as it was much easier to just connect the USB cable. One table controls your shift firmness and shift points. It was very intuitive.

http://www.usshift.com/usq4.shtml



Just my experience.