I too went thru this dilema when speccing up my car. In the end I went for it as I really wanted all associated with it (idrive, bluetooth phone book display, entertainment display) - and it looks great in the car too
I am now glad I did as it is a great toy and makes the whole car feel special every time you get into it.
I have not specced it on my wife's E91 320d Sport as it is a much cheaper car and will not benefit from it the same come trade-in time - I think!?!?!?