I should probably put down my initial thoughts of the device so far!
Firstly the audio quality. I'm quite picky about audio quality, having spent a fair amount of time and money on hi-fi separates, in ear monitors and headphones. I was a little worried that installing the DICE MediaBridge would result in a drop of sound quality from the CD changer. Thankfully, I needn't have worried. The quality is excellent, on par with the OEM CD player. The best quality is through the line out to USB connection from an iPod (as expected). What is surprising is the sound quality from Bluetooth (over A2DP) - noticeably lower but not that far behind and certainly much better than the OEM radio. I haven't tried playing audio files from a USB stick yet so I can't comment. I think Bluetooth A2DP is on par with the AUX connection - both quite clear and acceptable. Your miles may vary depending on your audio files. I was using mp3s at either 320kbps or in Apple Lossless format.
The interface is a little clunky but as I have the bog standard BMW Business headunit (i.e. no NAV), that was to be expected. The announcer, telling you which mode you're in, isn't actually that annoying but I believe there is an option to switch her off anyway. Usability with the rest of the system is very good. My girlfriend found it quite simple to pair up her Samsung Galaxy S2 to the MediaBridge to start streaming music from her phone over Bluetooth A2DP, taking over DJing duties from my iPhone 4S, for example.
We also did a test call while music was playing from my iPhone via USB and the music was interrupted with the number of the incoming call appearing on the headunit. The announcer also read out the number.
So in conclusion so far, the MediaBridge is performing to expectations and is a rather neat product. It is exactly what I was after and has impressed me with its ease of use. I'll report back in a month or so after an extended testing period and let you know of any updates!