I'm 32 and have been using computers and their various interfaces since I could barely walk - I was the kid programming the VCR and the Timex Sinclair when I was 7 or 8, and I wouldn't be where I am in my career if I didn't have an ease with clunky and/or downright awful interfaces.
The above isn't to brag, but to counterpoint the "electronic dummies and housewives" stuff before I say this: the '08 iDrive's interface is garbage. I test-drove it and then test-drove the '09 iDrive, and there's just no comparison. Since there were significantly better deals to be had on 08s, I really wanted to like the '08, and wanted to believe the people on forums like this one who were saying that the '08 was fine for non-edummies and non-housewives, but I did not find that to be true.
We sat down in the '08 and I asked the CA to show me what it takes to do what I consider to be a pretty routine task for a nav system: find the closest Best Buy and lock in a route to it. She eventually gave up. I took a crack at it, and after a bunch of pain, I think I was close, but we got kicked out of the car for another CA who needed it for a test drive. It was so ridiculously bad, at every step of the way - finding the right menu, finding the right place to enter the name of the store, finding the 'space' character, etc. It's far easier on my four-year-old piece-of-crap Garmin. It was also no problem at all in the '09. I don't really care about having the new shortcut buttons, but the new GUI makes a huge, huge difference.