Just got an Android based Samsung Galaxy S but before buying it, could not find much on compatibility of Andriod phones with Audi MMI interfaces. Took the plunge anyway, and thought I would share the findings in case it helps anyone else who may be looking:
1) For BT High, the phone interface does not allow a user to enable or disable RemoteSIM mode. If you pair from the MMI, it will "find" the phone and automatically pair with RemoteSIM enabled. If you want RemoteSIM disabled, delete the pairing and then start the pairing process from the handset and "search" for the car. In the MMI Phone settings, remember to set the Bluetooth to be Visible whilst pairing, it can be set back to Hidden afterwards.
2) With BT High and RemoteSIM enabled, any contacts that are stored in the SIM card will be visible in the MMI. However, call logs such as Missed calls, Received calls, Dialled calls, etc, will be blank on the MMI screen. The SMS text messages will appear on the MMI screen but this is inconvenient as they are stored in the MMI so you cannot read them later on the phone outside the car which is the way it is designed, it is not an Android issue. The external antennas provide better signal quality but only operate on the 2G frequencies, so you will better off in areas which have good 2G signal, but worse off in areas where 3G signals exist but no 2G signal. When RemoteSIM is enabled, the phone becomes "offline" so eMail and other features cease to operate on the handset.
3) With BT High and RemoteSIM disabled, or with BT Low, the situation is more encouraging. All contacts in the phone book become visible on the MMI screen. The call logs such as Missed calls, Received calls, Dialled calls, etc, will be visible on the MMI screen. You will not see SMS messages on the MMI screen, but the messages will be in the phone to read anytime/anywhere. The phone handset antenna will be used so whilst it may be slightly less capable than the external antenna in 2G areas, it will provide coverages in areas where 3G is also available. Other phone online features such as eMail continue to work.
Nothing to do with the A5, but whilst writing, I would say that all the 5 star reviews all over the web are absolutely right, it is an awesome piece of hardware!