Not too useful; but fun if you build your character right. A couple last perks allow you to strip enemies off weapons and armor; combine with Illusion spells you can sometimes laugh your butt off to the things the AIs do (fist fights, guards break into homes to grab random weapons...)
One time I took this Forsworn's sword and put it on a rock under the edge of a cliff of a fort in the Reach. He decided that he couldn't find any other weapon around, so he try to jump down to that rock to get his sword but he overshot and ended up hitting a couple other rocks on his way down.

. What a moron!
If you want to make money as a thief; it is easier just to break into homes, steal stuff and/or open lock boxes rather than getting frustrated every time your pickpocket attempt fail (90% success chance is the cap)