Pop'n Music 11 can't be played without a Japanese PS2 or Swap Magic discs and tools due to regional locking.
The game is overall difficult and fun, but the unlocking system in this particular installment is slow and rather painful. I've been able to play the game for just over a week, and I must say that I very much enjoy the game. It may take a while for new players to get used to if you only have Dualshock 2 controllers, but depending on if you have previous rhythm game experience, it'll come to you at a faster or slower pace.
There are 113 songs in this game, and there's a large variety of both easy and difficult songs.
My only real issue with the game is how long unlocking takes, but even then, it doesn't take that long to get Mileage.