I just killed my wife's X3's nav system (which is a Mark IV DVD-based system) trying to upgrade it. Here's what happened:

1) I downloaded the image file using the above link.
2) I burned it using Alcohol 120% version 1.9.2 at 8x (the lowest I could go - 1x was not an available option) on a good-quality CDR using the default options.
3) I booted up the nav system, then went to the back of the car, ejected the nav data disk and inserted the disk I'd burned. Since there was a message on-screen saying there was no disk (which appeared when I ejected the nav data disk) and asking me to press "OK", I went back to the front and pressed the right knob. At no time was the key turned off.

At this point I got the expected black screen with orange text saying "Note: CD-ROM in navigation computer, Loading software" but did NOT get the white and blue screen that usually follows showing the progress bar. Instead the screen went black and stayed that way. I've done about a dozen nav upgrades over the years, starting with my 2001 330xi, in 3 different BMW's so I've seen all sorts of things happen. I decided just to let it ride and that perhaps the update was occurring anyway. I stood at the back of the car waiting to see if the disk ejected for about half an hour, then gave up and hit the Eject button.

Fortunately, the update disk did eject so I was able to put the nav data disk back in. It would have been kind of embarassing to take it to the dealer with the pirated update disk in it! I also went back to the front and hit the right knob for good measure in case it was waiting for an "OK", but nothing happened. After letting the car sit long enough for the DVD drive to power down I turned on the ignition, but the nav screen is still black.

I guess we'll take it to the dealer with a mysterious malfunction to have them repair it under warranty. I will NOT be trying to update my Z4's system, at least for a while. The X3 DVD drive is MUCH more accessible, and if I got a disk stuck in the Z4's drive I'd have to disassemble a major part of the car to get at the drive to try to remove the disk. (I know this since my nephew once stuck some sort of disk he'd burned into the drive and killed it so that the nav system would not work nor eject the disk.)

It's clear that several people have used the same file for a successful update, and I've had success many times before with other versions. However, I'd urge great caution until a larger number of successes is seen.