Try it before you judge it.
True, since I dont own a car with Idrive nor have even sat in a new M5/M6 with all the Idrive performance features, I dont know much.
However, I have driven a 335i with Idrive and Nav and found it cool (a neat thing to show my buddies) but the Nav screen in the 3's clutters the dash board.
PS: Idrive is a love it or hate it device. However, most reviewers hate it hate it hate it. The Top Gear reviews of the M5 and M6 are actually funny. However, I am aware Clarkson is an A$$ and never gives BMW much credit.