From my experience in the beta having a full team of friends in a voice channel is when it's at its best. The coolest feature is that you are never restricted from choosing a character. We played around with having multiples of the different heroes. Setting up 6 Bastions can be devastating. :3
I would say that for full price it isn't worth it unless you will be playing with 4-5 friends on a consistent basis. It just isn't as fun without friends.
