traps are very useful and in ToB you get a few very powerful new ones.
however, most people resort to using traps to trap spawn areas, i.e. setting traps in exactly the location, where you know a tough monster is going to appear, or setting them around neutral monsters before they turn hostile (Firkraag for example). this in my book qualifies as ultra cheese and that's one of the reasons I only use thieves in a very limited capacity (after getting her back, Imoen is all the thief I need; if she's not in the party, then I just play without a thief).
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