A lot of gameplay for your buck.
The Concept: This game can legitimately be considered the father of the modern generation of Custom Music Games. Distributed through Steam, the game uses your music to generate a “road” with various colored blocks on it, with the color based on the intensity of the music and different colored blocks having different point values. You need to fill up a “meter” by hitting colored blocks and getting them to match in the main gameplay modes (with different “characters” having different special abilities that help make things easier). There's also Mono Mode, where you just have gray blocks and colored blocks, and you have to hit only the colored blocks, with the blocks increasing in value as you hit more.
The Good: The game supports basically every music format that you probably have in your library, as well as music CDs. The only formats I haven't tried on it are .ogg and .flac, but everything else has worked just fine. Controller support also works really well. Graphically, it scales well enough that it run smoothly on laptops as well as on higher end gaming systems. In addition, because of the game's popularity, leader-boards in the game are fairly well populated. Additionally, the game is extremely affordable at a $9.99 price point.
The Bad: The backgrounds are fairly monotonous. While it took, frankly, a year or two to get there, the essentially the same background essentially bored me, and started to make the game kind of dull. Also, not all the characters are balanced – in particular, I've noticed Mono characters are at a consistent point disadvantage to the other character types, and attempts by the game developers to fix this have failed.
In addition, while the game supports scrobbling to your Last.fm, it doesn't use Last.fm to authenticate tracks to prevent cheating – so someone could change the name of their mp3 of “Enter Sandman” to “Muskrat Love”, and use that to get a score on that song that no-one could beat. Track titles from CDs are based on CD text rather then CDDB lookup, which means that some CDs just don't work well with this game (particularly classical music).
Verdict: Definitely worth a purchase. Again, the game gets a lot of gameplay for its value.
Recommended Music : “Comfortably Numb” by Pink Floyd, from P*U*L*S*E . In particular, the game's extended guitar solo makes for a fantastic ride.
