I've used Signvox in the past and personally was not happy with it. I've since have started using
Podio and have been extremely satisfied. Though between the two (I'm going to lump Shopvox into this statement as well), the bar for entry for Podio is much much higher, as it is 100% customizable. So that could easily be seen as a positive or negative. But I've enjoyed much more being able to tailor the software to how we work instead.