In the LRs it is fairly basic and limited to telephone and music - all works fine and requires nothing more than a standard Apple cable. All phone functions are available via voice, steering wheel and touch screen as is full access to the phones music. Additional music is available via A2DP bluetooth streaming.
On the Mercs it's a broader offering - music and video available via the media interface with full album art and again all controlled by voice, COMAND system or steering wheel. Additionally it shows SMS and email on screen plus the data connection allows for direct interaction with the nav via Google Maps, web radio streaming, web browsing, hotel search and booking etc etc.