I like that the game has an ending but after a few times playin it through I would like to have an endless mode. A mode where there is no ending and you keep getting harder monsters and random floors. I think adding an endless mode to the game will significantly improve the replayability of the game.
And I don't know if this is on the ideaboard allready; classes (randomly given to you) would be fun. For instance, you could give a new player a random skill at the beginning of each playthrough.
Also, I like Dirahmer's idea of a scoreboard where all your playthroughs are recorded (time played, enemies killed, floors completed, etc..). Also scrolling with the mouse to select other items on your hotbar would be great. (also his thread)
Keep up the good work. I love the game!