I have used Lubegard and have faith in it.
Can I tell the difference in transmission shift quality? Nope!
But, it brought back a nonexistant overdrive and made one transmission's ATF very dirty in about 7k miles. This required another flush and bottle of LG and fluid has stayed spotless since. I guess that bio-esters clean well.
I don't see it as a waste of money.
But, I don't see the need for it when using a high quality synthetic ATF and reasonable maintenance schedules.