I would notice getting paid 20% more. I would notice paying 20% less for a car. I might notice if a script ran 20% faster. That's about the minimum percentage reduction in run-time that I'm likely to notice.

But, of course, this isn't even close to a 20% reduction in the run time of a script.

A much more apt comparison would be if you got a 20% discount on... the ashtrays in your car (only after subtracting out "overhead" so you really only got a 10% discount on the actual price of the ashtrays).

This reminds me of a cartoon from my college newspaper that showed a sign saying "50% off books! 50% off supplies! Total savings: 100%!!". You have to believe in magical math like that in order to find a 20% reduction in something that is a tiny part of your total run-time to be "significant".

Take a useful script and have somebody run it once with and once without this optimization. They won't notice that it ran faster. "Not noticeable" is well below "significant".