For as long as I have been in education we talk about the theory of multiple intelligences and the ways in which we learn.
For those who learn best visually, reading on twitter, blogs, and podcasts are a great way to access learning.
For those who learn best through doing, having interactive twitter chats and blogging on your own is an effective way to connect.
There are many people however, who prefer learning through auditory processing.
Voxer actually covers all 3 areas. You can interact verbally or through text, you can read and view pictures, or you can listen to great learning opportunity.
Voxer gives you a way to connect with your pln in another way. I have had the chance to put a voice to the name/face for many people. Learned about their ideas, their lives, and perhaps a bit more.
Many people, even those using it are unsure of what value it presents. I would say that it provides value in many ways, but most importantly, to help people connect in new and meaningful ways.