I did a test today with my free time. I downgraded to .171 and I could actually check my voicemail with a bluetooth headset while on UMA. It was not perfect, and I did drop a few calls but I did have a 20 minute conversation without a drop.

I then upgraded back to .180 and did a clean install. Connected to UMA and then paired my headset. I tried to call my voicemail and did not hear one word and got a call failed. I tried about 10 different times even after a battery pull, with no luck.

As a reminder, whne I am not on UMA I can talk for 8 hours on any of my bluetooth devices.