Recently we have a lot of new Vocaloids and I think it's great, although I recognize all of them from voice less and less. Some of them don't have characteristic voice to tell the difference. I can't say Mayu have characteristic voice although I can't compare her voice to other vocaloids too. I'm not a vocaloid specialist neither but I see one specific thing about her- she have yandere vibe.
Yes, the new vocaloid is a yandere and I even got scared when I clicked her face on her official site. One of official arts shows her choking the mascot with evil aura around her. In the box art she seems to be holding something in her right hand and when we examine the reflection we will see an axe.
Right, the design. Artist named Hidari drew her. He previously made a character design for Fractale and Natsuiro Kiseki and I must say I love his style. These new vocaloids have gorgeous designs. I like how they got some things connected with music in part of their clothing. Mayu is no different. She have a gothic lolita dress with amplifier buttons and keyboard, a disk on her hat and her mascot Usano Mimi serve as a microphone.
She is developed by Exit Tunes and her debut will be on 05.12.2012. As for her voice I think it's clear but as I previously mentioned I don't find anything characteristic about it. Although she sounds good in techno/trance songs. One of her demo song Mayuzumi no You na Sora Kara (From The Eyebrow-Paint-ish Sky) got on vocaloid ranking recently. She also got few original full songs, I would like to distinguish I Wish and Small Pupa in the Cacoon.