On the level where tapestries hang from some of the walls, I got very frustrated at one puzzle where I failed to find the clue to solving it. It was impossible without.
Turns out you can rip off the tapestries to reveal alcoves and buttons. ARGH. I could have deduced the possibility, but in a way it's bad design; at no other point does attacking the wall have consequence.
Another thing, kind of funny: I'm always hesitant to use single-use weapons like bombs because I'm worried I might need them against a hypothetical future monster that I can't otherwise defeat. And I always had them in my rogue's inventory because I thought that bonuses for thrown weapons applied to them. (Still not sure if they do.) Plus, my rogue was always carrying a bow or crossbow in one hand, and arrows in the other, so removing either one in favor of bombs would severely cripple my ranged offensive ability. Now I completed the game with about a dozen of every type of bomb, derp.
I haven't really experimented beyond the normative equipment distribution among hands. My fighter uses a weapon and a shield (the minotaur kept one hand empty), my rogue had either two throwing weapons or a bow and arrows, and my mage was carrying two magic artifacts at all times. It's possible to dual wield melee weapons - my fighter carried a fire sword in his off hand until it ran out of charges - but there's no advantage to it; the cooldown for attacks applies to both hands. If you use two different weapons you're just sacrificing the use of the most efficient of the two. At one point I gave a spear to my mage so he could attack from the back row, but that just meant I could cast spells less often. It's a shame, really, there's potential for some interesting gameplay variety there.