I'm not worried about getting away with murder, I was more curious if it is useful in dungeons to 'soften up' a boss before a backstab. Then again, I can't remember if undead can be pickpocketed or not..
I'd imagine undead would be impervious to poison anyway.
I have used it when I want to kill someone. I sneak it on their person. I get no fine by the way. I have however only used it about 3 times. Novelty maybe, I dunno. It is nice vs humanoid targets, especially bosses... virulent poison is 50 pts of poison damage. Then you can coat your weapon with another one, then go for the kill. I don't do any kind of crazy enchanting + alchemy + smithing so my daggers aren't doing hundreds/thousands of damage as I like to have more fun than minmaxing. But even 30x isn't giving me the one-shot I want on mini-bosses (3 such hits to take out a deathlord or similar humanoid miniboss). I'm level 42 I think... but my one-handed is only like 35 or 40. My archery is 80. Poison is really nice to coat those as you can only get 3x damage out of those bows. I have roughly ebony quality bows and arrows, no daedric stuff showing up. Of course I have most of the pickpocketing some for novelty (steal weapons/items from their person). If you join the DB it can be a fun way to kill your targets too. I seriously don't think I ever got a bounty for doing it that way. Although a lot of the time I just fury them (I have some illusion perks) and let the guards kill my targets for me. LOL