I was getting into that game, but I started to find a lot of the fun mini-games have terrible pc ported game controls that seem to make them incredibly difficult. It's that juggle of pondering if it's actually worthwhile to invest in a controller just for one freaking game.
As Keyrock said in an earlier post you can use a variety of different controllers (I personally am using an old XBOX 360 for my game). If you don't have any of those controllers then I still think that a controller would be a wise investment. There are many different PC ports out that have terrible controls on the keyboard but have outstanding ones on a controller. There maybe another game out in the future that may get that have an awful PC port but tight controller support.
PS.Yeah the mini game controls are the worst. Who in the hell uses I,J, K, and L for a rhythm game !?