Well it's all very good to begin with...
But then the later enemies almost all have Infravision or ESP of some kind, making it useless
Do NOT steal from Attnam by the way. It still alerts the town even if you are invisible, meaning that for one, you're probably dead (tougher guys have ESP/Infravision) and two, even if you do escape Attnam you've now railroaded yourself into getting the "Evil" ending if you don't end up dying along the way.
Stealing from the dungeon store can be gotten away with though. For added safety, make sure you have the keys to lock the door(s) and plan the fastest way to grab what you want in the least turns before sprinting to the door - even when they're bumbling about while alerted they can attack you if they attempt to walk into the same square as you.