Buy the option for the iDrive features, not the navigation features alone.
iDrive helps so much more for:
- Media management
- Additional climate and vehicle settings you would otherwise need to code
- Phonebook/Bluetooth management
I also find the built in Nav useful for navigating around traffic during my morning commute. I have 2 shortcut buttons to automatically guide home and to work. It will warn me of any traffic backups and I will take different routes. I don't like google maps with my iPhone, since it will route me, but not tell me what the traffic backups are - only red lines.
Those who say it will look out of date in X amount of years...perhaps, but I would rather have this than some aftermarket GPS unit plastered on the windshield - makes it look like a rental car. The worst are the E60 5 series with the iDrive hump and a Garmin unit plastered on the windshield.
I personally don't mind the GPS units on the older vehicles. It fits with the rest of the out-of-date interior. I can't say that peeling buttons on an E46 interior are "classic" while the nav screen is horrid. The whole thing is classy but obviously shows it's age.
It all comes down to personal preference / wants / needs. If you just need nav, iDrive isn't the best. If you want all the other features, it's wonderfully integrated into the car.