From a cute, leek-bearing 16-year-old with pigtails to fun-loving 14-year-old twins to...wow, a 20-year-old? The newest Vocaloid character, who (as we reported) was based on Yuu Asakawa is a real, honest-to-god adult, Luka Megurine.
The idea behind the voice is to be more “cool, mysterious” and mature, rather than cute and innocent like the two previous releases. I'm on board there, but honestly, I don't think her design is as compelling as Miku's, or even as the Kagamine twins.
Luka can sing in both English and Japanese; I don't see a demo song up on the site, but thankfully there's one up already on YouTube. If you want to compare it to Asakawa's normal singing voice, try the image song for Fate/Stay Night's Rider, or her song Tsuki no Gotoku.