I can get addicted to certain types of games very quickly. It happened with Guitar Hero 2, Audiosurf and Rez. I think that there is something about rhythm games that attracts me to them.
I wanted to try Frets on Fire for quite a while but because I have a laptop it would be a major pain to play with my keyboard. It was a while later that I discovered that I could use my XBox GH2 controller. So I dug it up and decided to give it a try. I was surprised to see how easy it was to get the controller working on a PC (just plug it in, wait for the drivers to install, and you should be able to configure the keys in the game)
The game comes with 3 songs to choose from each with its own style and difficulty. However there is an active community dedicated to creating new songs for the game (Just search online for Frets on Fire songs) so there is always something new for you to play. You can also create your own songs using the song editor.
The game is very responsive to the notes you play both on the keyboard and with the controller. If you have played any of the Guitar Hero or Rock Band games you should be able to just pick it up and play. However, if you're new to this type of game, there is a very funny tutorial.
There are some things that could have made this game slightly better such as a multiplayer option, whammy bar and better backgrounds. These things all might make you lean more towards the commercial games. However, because there is infinite possibility to play new songs, this is slightly more than you're run-of-the-mill clone. I would highly recommend this game for a quick fix of fun.