The game's best selling point is if you can find some of your favorite songs mapped out. As the difficulty increases, the orbs get smaller, appear with less time before you have to hit them, and do more creative things (assuming the mapper had shit for brains, sometimes they can just be lame)
A map done well can be great fun, but I've hit one or two that just make me want to stalk the creator, steal their credit information, use it to withdraw enough money to travel to their current residence (And possibly buy some Doritos), tie them to the beams of their house, and set it on fire, and watch the life leave their eyes as the fire cooks them alive.