Voiceful falls down in three major areas - art, story, and yuri.
The art is, although not of the traditional cute manga style that one would find in more popular manga like D.N.Angel, Fruits Basket, and anything by CLAMP, has no great appeal or substance to it. Not only do the drawings lack the quality and subtle detail of the aforementioned manga, but simple things like expressions never seem to have any life to them. The story isn't original; scroll up to the synopsis for a brief summary. Of course, even the most tried-and-tested stories can be written beautifully, but here, the four disjointed chapters rarely make sense, and the feelings between the two girls have no life in them at all.
Which leads me into the yuri part of my review - basically, there is none. The author even apologises for it and the end of the manga. You'd have thought that something that was published in Japanese magazines Yuri Sisters and Yuri Hime would have more yuri to it. Unfortunately, you'd have to really use your imagination to picture anything between these girls beyond friendship - not that the manga really lends itself to the imagination.
However, good points are that the volume contains some bonus stories, both related and unrelated to Voiceful, of about the same standard as the main feature. Also, there is a guide to Japanese honorifics and some translator's notes in the back, which are wonderful if you're still new to manga. I don't remember Tokyopop doing this...
At the end, there is a preview of another, much better looking manga called "First Love Sisters". It looks much more charming, and someone else on amazon has already given it a good review.
So, overall, a disappointing manga, and definitely not recommended. Although I haven't read it, it would seem First Love Sisters would be a better alternative - unless you can find Kashimashi somewhere...