I've seen the "Antenna Error" two or three times since I've owned the car. It's always worked fine after a soft reset (let the car go to sleep and restart). I don't know if it's a SW or HW issue, but I'm inclined to believe the former, since when it works it always works perfectly. It seems to be an initalization issue.
I also saw a "Can't get a satelite signal" message for the first time, when I parked in the bottom of a parking garage, but the Sirius came on just fine once the car could see the sky.
I've been wondering why there is no 'off' switch for the radio/aux... every other car has it... and it would be nice to save that extra wHr of power...
My Mercedes was the same way with the COMAND system. There was no way to turn off the radio independent of the entire system. Mute or picking another input were the options. I didn't like it then either, but as least I'm used to it
I really like having BT audio on the car. Between Pandora and TuneIn, I don't think I'll be re-upping my Sirius subscription when it runs out. Plus, being on BT audio allows me to 'turn the radio off' by closing the audio app on my phone.