I'm mixed on illusionary walls - for people well versed in the genre, they're kind of fun, especially in a well-made, tightly-packed dungeon where the empty spots on the map can clue you in to where they might be. For people not well versed in the genre (my first two people I watched play it), even with really strong hinting they just don't ever find any of them, or even really think to stop and look, so I think it's maybe something best lest out of the genre if we want a larger audience to enjoy it... I also made the mistake of requiring an illusionary wall to progress at one point, and even with the newly edited, giant crack down the middle, sprites, some people can't find it ^_^.