I've noticed that a lot of people have trouble finding secret doors at one time or another. What about adding an item that reveals hidden areas? It could be a potion that automatically reveals secrets within a small radius of the player for x minutes, or perhaps a one shot item that reveals either a single secret at random or all secrets on the current dungeon level.
Alternately (or additionally) there could be an "Obelisk of Revealing" which would have one of the effects listed above. Maybe it could even allow you to see invisible enemies from farther away...