The reason of their rant is that iDrive has the steepest learning curve of all car user interfaces out there.
However that learning curve shouldn't take you more than 2-3 hours. Honestly.
Once you know how to use iDrive, it's the most intuitive and easiest system to use.
I have driven several cars recently - BMW without iDrive (loaners) and other cars, and I always miss my iDrive.