Having listened to Haruna's MC from the DMM concert, she's definitely coming off as slightly hilarious. xD Esp as she messed up (I could post it somewhere, but it's very quickly/sloppily translated and stuff...)
But. Boring or not...
Haruna is good enough when she gets her low songs parts in songs. Same goes for Erina. No, Erina can't pull off "Otome no timing" because it's too high. Nor can she pull off "Boogie Train '03" or that song she sang in Hawaii because they're way too goddamn difficult for her and she has no idea of how to breathe properly etc.
But give her two/three lines or whatever in songs that are on a low-ish key and she'd pull them off well. As would Haruna. Haruna will probably grow to be better than Erina will though, but right now I wouldn't say that she is.
My point though, was that Aika is am okay singer. Thing is that she gets these cutesy painful songs that make her sound awful as her voice is not one that sounds good on such a high key. She did a duet with Reina (
Suki ni nacchaikenai hito) on that Sayumi/Reina/Aika bustour and she did
great. Because that song is on a low enough key that makes her voice sound less strained and... well. Good.
Doesn't make her any more
fun or what you guys ask of her, but she
can sing and is way better than Sayumi/Koharu/Erina/Haruna -- and if we're going senpai she owns Rika by far, too. And in my book I'd rather listen to an album of Aika than any of Kaori's, but that's a preference rather than ability to sing, I guess.