Fun game that lets you get a new experience from your music library.
Expert mode was pretty challenging on many songs and will give your fingers a workout. I've only tried it on my computer keyboard but it looks like you can use a USB guitar controller as well. The leaderboards add a nice metagame to your gameplay along with the always fun Steam Achievements.
Songs with a strong beat work really well in this game as it picks up quite well. It came with 8 features songs from what I assume are indy bands. But of course you're going to want to add your own music.
The backgrounds are pretty crazy at times. It's only $10, so if you're interested its worth a try.