I'm not sure of the technical details, but it seems like it could make some graphical things more accurate. Note that I say this because in Dragonball Z Budokai Tenkaichi 3, it fixes some of the missing polygons on characters, but it does not fix them all. It's also reported to be slower.
I also heard that these options will eventually replace the existing VU Recompiler options? That I don't know about.
It'd be good to hear a rundown on what, exactly, it does.