I'm signed up for the Low Light Pistol Operator class at the Sig Academy in August so I will be putting the DIY Finger Lanyard to some more testing. I'll be bringing a couple of Malkoff lights fitted with the lanyards.
So far in EDC use and doing some informal testing at the range, they work well. Being able to retain the light without actually gripping it is certainly a major benefit. I also like that I can place the lanyard in the pocket to keep it from catching on anything, positioning it so I can slide my index finger through it when reaching for the light.
Regardless of what you use, practice makes perfect.