I've seen this question speculated on so thought I could pass along some info.
I guess I only really know about the Bluetooth enabled radio in the 2008 Nissan Versa SL. In Canada it is part of the "Technology" package, I think it is part of the "Convenience" package in the US. Althogh I suspect the information is valid for other vehicles and model years.
This radio only supports the Bluetooth handsfree profile. This means, it is only good for calling functions on a Bluethooth enabled phone. It can not be used to stream stereo music to the radio from a Bluetooth enabled MP3 player using the A2DP profile.
I've also noticed an issue with my iPhone 3GS and my Versa that did NOT happen with my old Razr, Blackberry or LG phone in the same Versa.
There seems to be about an 8 second lag between when you press the button to answer an incoming call and when you and the caller can actually start hearing each other. This really sucks, and I suspect it is a bug with the iPhone that I hope will get fixed soon. I've tried two different iPhones, a 3gs and a buddy's 3g with the same results.
Apple has many problems with their Bluetooth implementation .... I hope they get their act together soon.
I actually regret paying to get this upgrade 2 years ago when I bought the car now that I see how cheap some of these after market decks are that have really good iPhone integration. $280 can get you a deck that does Bluetooth handsfree phone, Bluetooth A2DP stereo music and a USB hard wired connection for control, music and charging.
