I just installed a Dice Mediabridge in my 07M35 and am pretty pleased with the results. If you're not familiar with it, the MediaBridge has native Bluetooth A2DP/AVRCP (confirmed working with an HTC One), a 3.5mm aux input, and a USB port that supports flash drives and Apple devices. It also includes a microphone for use as handsfree through the stereo, but I am not using this piece since I'm linked to the bluetooth in the car. You can currently pick one up for $70 at Amazon
http://www.amazon.com/Dice-MBR-1502-NIS ... B004Q3RDD4
I used the Bluetooth connection with my android phone for a couple of days, but I thought the audio quality was subpar. The volume was fine, and I think the mediabridge puts an emphasis on the bass and treble. The mids felt lacking, but it is very acceptable for short drives or when using navigation from your phone. The steering wheel controls allow you to change tracks through the bluetooth connection... pretty slick. I did not have any track information through Bluetooth. For reference, I have never heard any streaming bluetooth that I thought was acceptable.
I am now using a 3rd gen ipod touch through the USB port. The audio quality is at least as good as the MP3 cd's I was using, and I plan to make this work for me. My track information is hit or miss, but I expect I need a firmware update on the mediabridge. I will confirm this weekend. Steering wheel controls also change the track on the iPod.
Installation was very straightforward, and I have my unit sitting between the gearshift and the cupholder. Access for firmware updates wont' be too big of a deal. All of the cables are included, and there is no need for any splicing of wires. For the low entry price (specific to the model that happens to work in our cars), I highly recommend it.