I am in the UK and have Navigation Professional. I just got my E90 back today (30/01/2006) with the CIP 20 MP3 upgrade. I can confirm that both the in dash CD and DVD drives now play MP3 disks ok
I was NOT charged for the upgrade as it is covered under warranty. Make sure your dealer does not charge you for this upgrade. If you don't complain then the dealer may try and charge you £150 for the upgrade. Take no crap from them and don't pay them a penny!
Also noticed that I-drive is faster!