For most idols, the solos are... actually pretty good, except for one little thing: The "usotsuki" before song's end. Haruka, Yukiho, Chihaya and Takane feel like they're the only ones who don't have completely flat "usotsuki"s. (The Futamis, I'm on the fence - theirs isn't flat, but it doesn't seem to actually... help.) Overall best solos are Chihaya/Takane to me, though.