I don't doubt that a simple spring change can reduce DA pull weight by as much 50%, I've seen it. When someone claims a $20 spring kit "turned my plain Jane 75B into a Shadow Orange", well that's just silly.
It's a cheap spring kit, nothing more nothing less. It doesn't reduce trigger travel, eliminate the fpb, or shorten and smooth hammer hooks. Implying that there is some "magic" to be found here is a disservice to new people that come here looking for credible information on how to improve their pistol.
I've done a couple trigger jobs for friends with limited budgets. Just springs and polishing, no race hammers or short reset kits. While they were happy with the improvement over oem, they don't compare to a full trigger job with quality parts.
The true test will be when users actually put several thousand rounds through Mcarbo equipped guns.