It isn't useless persay, it is just outshined by many more useful powers. It's a flat -20 to those systems. The general consensus I've found is that specializing in stealth for MES is not a cost effective use of your skill points vs. the benefit you'd receive.
It sure is. I've just been dicking around with that ens slot on my AE, retraining my boff on a whim to try out all the sciy ens powers and was going to give MES a shot next. If I can approach a group of mobs undetected even with 0 ranks of Stealth, then it serves its purpose.