I'm starting to put points into the 'detect illusion' category. How does this work? Does the thief automatically check for illusions? Do you have to have the 'find traps' button going? If you have a good score, would it be best to have the thief just sitting back detecting illusions, instead of meleeing? Can he shut down opposition mirror images, etc?

Hmm ... the other skills are more useful in my humble opinion
No
Yes
I've used that strategy with some success using Jan when fighting illusion-happy mages.
Yep. From what I can tell, it seems to work rather like a True Sight spell centered on the thief with the same range as his vision.

I never used that... i might put some points into it today... how many point should i put into it to make it work good?

You'll never need more than 100 points in that skill. In my game Jan has about 70 in that skill and it seems to work fine, perhaps later on you could pump it up to 100 though. I actually find it to be a deceptively useful skill it's very good against people who like to go invisible and backstab so it is worth putting points in that skill IMO.

Hmm ... the other skills are more useful in my humble opinion</font>[/QUOTE]My single-classed thief is getting up there in levels and I have as much as I want in my other abilities. Has anybody ever found a need to have more than 100% in find traps, lock picking? I haven't missed a lock yet thru Chapter 5. I put 110% in find traps and I still never located the ...spoiler...
*
*
*
*
*
traps in Bohdi's lair in the spike room. Other than that, I haven't missed any traps.

Those traps, IIRC, cannot be detected by any means. Even the cleric spell "Detect Traps" cannot see them. I also do not think they can be disarmed; you can only hope you avoid them. I finally figured out a path by which I rarely take any damage through there.

Icewind Dale, also, was bad about having non-detectable and non-disarmable traps. Most of those were monster spawns, though.

Cheers,
-Sazerac

And you are correct, Sazerac.

Note that these traps are spear-type traps. Stoneskin is their bane. ;)

detect illusion!? i've never actually put points on that. i just started a new game last night as a thief with 120% in pick pocketing... IT'S GREAT! i've stolen about 8000 gold worth in an hour, although i haven't found a place to sell it yet, but at least my team is well equipped!