It's definitely a software issue, but who knows whether they'll be able to speed it up. I doubt it.
Mine is slow from time to time like you described -- suppose you want to go up to the menu above, you move the controller up, but... nothing. Hit up again. Still nothing. Then after a few seconds, it goes up. As if the whole time, it had been saying, "Hold your horses, I'll get to it." WTF?
This behavior seems random. It's not always like this when I start up, or always like this when it is accessing the DVD or whatever. It's completely unpredictable when it decides to slow down. I attribute it to German electronics quirkiness.
Only happens maybe 5% of the time I'm using iDrive, though, so I can only give 5% of a complaint to it. The other 95% of my experience with iDrive, and the way the car drives more than makes up for it.
