Without going too big into details, every item you pick up loot will incur penalties to your rolls, and its based on the item you are picking up. You will have to have a very good Move Silently (and Hide without invisibility) to even stand a chance, and probably need some luck on the rolls too. Even picking an herb incurs a -8 on the rolls. To make it even harder, sometimes i have picked an herb in a room full of enemies and passed like 30 rolls, and they still head over in your direction and follow you for a short distance. If you can succeed at it, the challenge justifies the XP, and many times its much easier to just take out the monsters as you go, but its awesome to be able to play the sneak if you want to try your luck.