At first I just played the demo, even though it was just 2 songs available, I spent at least 3 or 4 hours on them because I enjoyed them so much, and when I got the game i couldn't believe how much more there was. Not only do you get all these songs to play, you level up characters and can unlock new ones and there are even more songs that can be downloaded. I've already gotten over 100 hours of gameplay and still havent even unlocked all the characters, but that's probably due to wanting to level them up too.
If you're a fan of Final Fantasy music, get this game. Even if you're not that good at rhythm games, the songs on basic mode are easy enough for anyone, and the songs on ultimate mode are great for people who want a challenge.