As far as games go, one of the most important apsects of a long-term success is keeping the player stress-free. The more fun a player has in the mod's world, the more likely they are to play the mod again and/or recommend it to a friend. If a player dies repeatedly on level 1 because they are dazzled and confused by the knotty graphics and unusual collisions, that's usually not a good sign.
Made in approximately one week by a single person and little sleep, Shadow Keen represents a true milestone for mod production--setting records for speed, execution, convolution, and substitution. There is a LOT of stuff to do in this mod, but not a whole lot of incentive to do it.