I must admit to still having NEVER finished KQ3...It's the first adventure game I ever played and I never owned it, I always played bits and pieces at a 2nd cousins years back.....I'm going to attempt it without a hintbook, but having not played a game that hard for years, I dunno how successful I'll be.
And the worst bit of KQ4 for me(though I think I cheated quite a bit after this) was figuring out how to climb up the STUPID whale tongue. My mom, sister, and I kind of played KQ4 together way back when, and that one had us stuck literally for months. I should point out we ordered the hint book from Sierra because of it and it didn't help since it didn't give specific intruction(from what I remember) for climbing it....but everytime we got stuck too long on a puzzle after that, we found it far too tempting to cheat and ended up using the hintbook on other puzzles, fairly often.