While testing the OBi100 during one call I was simultaneously downloading a large file and uploading a similar sized file. While I didn't notice any distortion, the party on the other end said the conversation was "choppy" to them.
I went into my router's Quality of Service (QoS) screen. I added an entry for the MAC address of the OBi100.
When there is an active conversation the WAN bandwidth looks like this.