Here are a few quest bugs I found playing today:

1.  Treasure Map Quest:  This is the map that is initiated on a quest tile when you take a map from Darklings.  The quest is to find the treasure chest.  I visited the tile on the map with the treasure chest, but never received anything and the treasure chest tile simply disappeared and returned to a normal grass tile.  The quest is still active, but there appears to be no way to complete it.

2.  Blight Scroll: This quest is offered by the little guy who visits you after you answer a riddle.  I went to the tile and proceeded to lose to the apprentice mages who cast despair (the mouseover on Despair said it was 36 points of damage per level!?!?).  Despite losing, the game acted like I had won the fight and I received all the rewards of the fight including completing the Blight Scroll quest and receiving the Blight Scroll.

3.  Rain of Arrows still has a delay of 15s or so on many, but not all, of its shots.