It "fixes" your LEDs to look correct. It's one of those things where if you never use one you'll be OK, but if you use one you won't want to go back to the old way. For most games you don't really need the GI one, just the controlled lamps one.

Although for a game like TOTAN the GI one is a must because of all the animating of the GI it does. It goes from a strobe fest to what it is supposed to be.

Definitely a must for stern spiderman since it does that thing where a lit shot will be a brighter light than the others.

It's sorta like Color DMD, money willing just add it to every machine you can. Although I would prioritize Color DMD over LED OCD.