There has been a noticeable amount of creep on every one I've tried. I don't recall the actual measured weight before installing a Blackhawk spring kit.
After installing the spring kit I realized that I gained nothing from the mainspring change, and before bending the hooks of the Wilson very little from the trigger return. It was a struggle for my hands to compress the Wilson Blackhawk mainspring to get the pin in. That should have been sign enough that it wasn't going to be worth the trouble. I have since devised a small clamp to use next time.
The trigger return is very easy to replace. I don't mind tweaking springs to get desired results. The creep is much less noticeable now and the pull weight on mine measures 1.75 lbs. It feels much better.