Ok, so now that I've been playing this for a while longer :
It's a lot more linear than the original. I guess that was to be expected, since this one has a stronger focus on the characters and their personal stories. Pretty much everything from the original game and Live For You! is there, but downscaled and simplified. There's only 3 training minigames available, one for each of the 3 stats (visual, vocal, and dance). These are basically the same as the equivalent ones in the original game, but simplified and redesigned with the stylus in mind. The touching sequences are still there of course, and there's some new ones where you have to move a 3D model of the main character's head in a certain way with the stylus.
Idol ranks and idol levels aren't very important now. You can't pick which category to audition for, but the only thing winning an audition is good for now is to move the story forward. Also, you can't audition whenever you want. An audition is only available after going through a certain number of "important" promotion events (marked by a "!").
I'm impressed by the amount of voice acting in this game. Almost everything is fully voiced. The exceptions being the new secondary characters and the non-important promotion events. Then there's the 10 songs in the game (more like 30, since each of the 3 main characters sings each one) on top of that. The 3D dancing sequences look pretty good considering the hardware. Also the large amount of accessories and various costumes in the game, so there's quite a bit of content.
Finally, there's the network versus modes with leaderboards, which play almost exactly like L4U!, except that there's only 3 types of cheers instead of 5. Unfortunately, these modes are local wireless only.
I'm enjoying the story (at least the one for the character I'm playiing with), but I miss the more arcadey gameplay of the original. Maybe it wouldn't have been so bad if the multiplayer was internet-based and Nintendo's online infrastructure wasn't so poor. Oh well, glad I bought my copy for half price.