Since we had the old iDrive in the 7 Series, the iDrive in the 07/08 X5...I think this iDrive in my 2011 35d is awesome. The quick buttons (Radio, Tel, Nav, etc..) are great and the options for all the settings and choices has been reduced to a practial and useful amount.
We had the Mercedes' version of iDrive in the S-Class, and I greatly prefer iDrive. I really like using it in my 35d! Actually could not be happier!!