It isn't, unless you find a VERY dark space, and have it level 4 or maxed, but then that would go against the "no camping" rule, so, save invisible for the last skill maxed. Low grav is cool, to get to places when it doesn't allow hook on the map, but it's pretty useless, because we have hook. These are the skills you should max first (In this order is the best, but you can spread it out):
Crit, Hook, Hp, speed/knife, regen, low grav, napalm, invis.