I think people were playing about with home made additives for years , chucking ecover in the water, isopropanol, rinse aid etc. One guy on here even chucked some white spirit in his tank! (don't try that one).
I don't think any of them could possibly make a massive difference to cleaning speeds, same as hot water doesn't make a huge difference most of the time.
GG4 seems to give an edge to the result, not much but enough to add a bit of sparkle. Seems to thin the water down a bit on the glass. Titan Labs say it has an ingredient to combat calcium deposits, as I live in a hard water area I'm hoping it might break down the hose pipe spots and mineral deposits we get.
Vision seems to work differently from what I can gather as it would appear to change the viscosity of water and make it gloopy. Sounds like it might float to the top of the tank too as people report the bubbles increasing towards the end of the day.
I've never used vision, just what I've read on here and other forums. The guys that use it seem happy.