[xDrive50i]

AFAIK, BMW does not offer a CD changer anymore but rather a DVD changer. You do not really need a CD changer since you can transfer your CDs onto the systems HDD which makes selecting a song or album a LOT faster than changing a disc in a changer. It also gives you the ability to put a LOT more discs into your car compared to a 6 Disc changer. The reason the entertainment package comes with the 6 disc DVD changer is since DVDs take up a LOT more space than music and since the system HDD only has 12GB available for misc storage, you wouldn't be able to store a lot of movies on it. There are also legal issues involved in copying movies that I'm sure BMW obviously doesn't want to get into.
I use the DVD changer for kids movies so that my kids can select and watch them while we are on the road and use a USB stick for my music that I can listen to (also while the kids are watching their movies with the wireless headphones in the back).