Thief already has less skills than other classes, so if i play as a thief, i try to use every skill i can get...
I used them because they are very good addition to the thief class.
I didn't put anymore points into the skill - as i said, 1st level of the skill gives 100 level scorpion and i was using them when i found them (didn't buy them, but didn't want to carry them, when i found them, they weight more than they cost; so i used them, just so that i didn't throw them away, they look nice <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> at low levels when i found them, i got 1-3 scorpions, in wastelands i got 10 scorpions per find... used them and the whole level was clean in a jiffy - and i still had my skill at 1st level. I wish i could drop their level to a 5-10 times smaller (100 => 20 or 10), that would balance them and would make skill more usefull (in the terms of putting points into it). Right now it's broken, no need to put points into it after skill level 1 even when you are above level 42.
Btw, other traps are too weak, but maybe it's just because i had skill of 1 only <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> ... 20-50 other traps are nothing compared to 1 scorpion, that's very unbalanced too.
P.S. I did hear other people saying something like "don't use scorpions, they are broken" or "scorpions will get you through the level with no effort" and so on... so it's not just my opinion.