I gave this a 5 immediately for the 2nd prompt. I've never seen a flash game with variable keybindings. You even allowed for changing whether UP is diagonal or straight up - never seen that in any other game period. For all I know this game is awful, but this alone deserves 5 stars.
Two things I found frustrating.
1) Sometimes a mob would become invincible at some point during the level. No matter what I did, its health would stay the same. If I killed all the other mobs, the level would be complete but that invincible mob would still attack my units and defense unabated until I killed the last enemy, which was a real deterrent to skull collecting.
2) When I cast fear, sometimes it would let me hurt the assassins with my icebolt, and sometimes it wouldn't. I don't know if it was intended for fear to cause the assassin to unstealth, but consistency would be nice as well as in-game tooltips to let the player know what's what.
 "Stealth Hunter 2"){kind=icon}
 "Epic Stand"){kind=icon}