Sham's got some very interesting thoughts about the thief over at his Grog 'n Blog, and the use of dice rolls to overcome obstacles:
Too many hidden traps which go off unerringly, damaging the characters and slowly (or instantly) whittling away at their hit points and resources become something other than traps. Such traps become abstract, losing their identity, reduced to mere collections of numbers.
The very notion of removing elements of deduction and logical thinking is the antithesis of the Empty Room Principle. Spot check? Not on your life, unless you either tell me you are specifically looking for something, or I, as referee, judge that your character might have a chance, not a static number, of noticing something based upon the prevailing circumstances.
I couldn't agree more. When the Trollwife picked a magic-user for her a solo character, and then had to negotiate traps by investigating them and finding logical ways to disable or avoid them, it created some of the best dungeon-delving I've ever run.
So the thief is on the chopping block for my Moldvay/Cook/LL hack. If somebody wants to play a stealthy fighter type badly enough, I'll make it happen for them. But I've got some ideas in mind for skills that might just make the thief obsolete anyway.