It is true that Mercedes is lagging when compared to other German manufacturers as far as recretional electronics (music, gps etc) are concerned. Their problem is that they do not make any effort to change the entertainment package of the car as time goes by and the expectations of the driver change. I would prefer a decently engineered car to one with the flavour of the month electronics.
The best cost effective method for our slks' seems to be the standard audio 20 without the cd player (so you do not have any MOST connections as far as the head unit is concerned) and then just buy a decent aftermarket system.
With the asking price of the command system (4000 Euros in my country, about 2700 of her majesty's finest pounds
) you can get a very good aftermarket navigation / multimedia system with the newest electronics.
I know there is still some resistance from the more conservative part of the Mercedes customer pool to keep everything in the car
in factory spec, but times as well as customers' expectations change.