Just previewed in Famitsu:
Seems to be based off of Pop'n 15, Adventure.
Finally, a cheap way to play the game. Beats shelling out for one of these:
It'll have 3, 5, 7, and 9 button modes, and around 80 songs.
For those unfamiliar with the series:
http://www.youtube.com/watch?v=ifVBfsNXl2Q
Hit falling notes to a beat with colored notes and various characters. Pop'n has an eclectic OST, comprised of everything from J-pop to jazz to metal to hip-hop and such.
Not sure how it'll convert to the PSP's control scheme, but it worked well enough for DJ MAX.