V801 makes Techniques cast faster by removing the ends of their animations. Instead of completing the casting animation, your character will perform about half of it, stop, and then launch the Technique. It's super ugly, but it does work. It's sort of a ghetto God/Battle that Sega didn't bother to code correctly; it removes every frame from the end of the animation, rather than removing every other frame to keep the whole animation but make it faster.
It's particularly useful at low levels to speed up Hard Techniques whose animations take forever; unless you're a Force trying to TA a quest where the decreased casting time allows you to stunlock enemies that would be able to retaliate if you weren't using the unit, V801 is relatively useless with level 30 Techniques compared to say, level 10 Techniques (since casting time decreases automatically with higher Technique levels).