So, since the April update I've lost 5.1 audio on everything but blu-ray. I put in a service request and they replaced the Xbox & received it today. Well during the setup process everything was fine until it updated. Now I am stuck w/ stereo surround again. This is definitely a software issue at this point that I hope they resolve in the next update. On a high note the swap out process was painless and only took 3 days..