Ranko's is what I expected. Her voice is really nice though, but it's a bit more cutesy than the mental voice I had for her.
Miku's, on the other hand, is not what I expected. XD
I wanted something more... Bizarre for Kirari. She's a giant idol that likes yelling Nyowa and other random things, but her song sounds pretty average. I'm sure it will grow on me though, because other than that I have no complaints.
Mika... I think hers will take the most getting used to. I thought it would've been cool to have an "answer" song to dokidoki rhythm. Oh well.
Uzuki's is really cute! It's a little generic, but... Whatever.
honestly, most of these will grow on me. I remember really not liking 1-5 when the previews were released and now I have 4/5 on my iPod. And dokidoki rhythm, my least favorite at the time, has an insane amount of plays.