Okay, consider this a nitpick; however while on the road yesterday, I noticed that an incoming call was missed and hadn't rang my stereo. I have a Pioneer AVIC-X920BT that I connect via Bluetooth to my Nokia N9.

I can use it for voice calls without issue. But Skype? Doesn't seem like it.

Also, noticed that my WP7 and Android phones both would show name/number when the phone call was coming in, whereas the Nokia N9 only shows number. It seems like the phone hasn't granted access to the contact list/address book like WP7 and Android had. I've disconnected the connection, paired back the stereo to the phone, nothing changes. In fact... come to think of it, I remember both of the other platforms asking me if I wanted to allow the stereo access to the contact list, whereas the N9 didn't prompt me of a such thing.

Edit: Weird thing though, I can use Bluetooth audio through my Jabra Extreme2 headset - but so far, only via wi-fi (to be honest, it's the only thing I've been connected to while testing this so far, so that might not be 100% the case here)

This... bothers me actually. Anybody else? Would love to route my phone calls via Skype while traveling also through my stereo too.

Hmmm.... haven't tried Skype in the car yet so I can't test that.

But I have noticed a difference in the Bluetooth Audio connection to my factory Nissan Juke from the N9 as compared to the N900:

With the N900, the calls and the ringtone from the phone would come through the car's speakers just fine, but the contacts were unavailable. I would need to manually speak the number or bluetooth transfer the contact card to the car one at a time.

On the N9, when I voice dial, it searches the entire N9 address book without ever prompting me to transfer contacts from the phone to the car. On incoming calls, the name and number of the caller are displayed.

This would indicate (on the Nissan system anyway) that the N9 grants full access to the phonebook over bluetooth where the N900 did not.

I've also noticed something else. Every other time I connect to my stereo, it doesn't ring through the stereo, just through the headset.

It says that it's connected to the stereo, I can see the number on the screen, but cannot hear anything. I have to switch the audio to the device, then switch back to the Bluetooth - and if that does not work, I have to turn Bluetooth off on the phone, then turn it back on then it'll play through the stereo and I can use the hands-free that way.

I've had issues with streaming Bluetooth audio from the N9 to my stereo, but I had issues with Android and WP7 - iffy at times.

Is it a stereo headset that supports a2dp?

I've had issues in the past when I've paired my iTouch4g with more than one device.
And then used a2dp on both of those devices.

Sometimes if a BT client (in your case the headset & car stereo) is multi-pair...
It doesn't support multi-pair of exactly the same profile type for more than 1x device.

Yep. It supports A2DP and AVRCP. There's no multiple pairing going on at the stereo. Just phone or nothing.

The Nokia N9 is usually only paired to either the Bluetooth headset - which I leave at the office normally - and I drive in the car sans headset, use the stereo just in case since I hate holding a phone up to my ear at anytime. But rarely do I have the phone with the handset in the car alongside the stereo.

So that's not exactly the problem. But there is a problem. The above method is what I've been using for almost a year on other platforms without incident. N9... probs.